Diff: iothubtransport_amqp_twin_messenger.c

Revision:

39:e98d5df6dc74

Child:

50:f3a92c6c6534

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/iothubtransport_amqp_twin_messenger.c	Fri Aug 11 14:01:56 2017 -0700
@@ -0,0 +1,2132 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include "azure_c_shared_utility/optimize_size.h"
+#include "azure_c_shared_utility/crt_abstractions.h"
+#include "azure_c_shared_utility/gballoc.h"
+#include "azure_c_shared_utility/agenttime.h" 
+#include "azure_c_shared_utility/xlogging.h"
+#include "azure_c_shared_utility/uniqueid.h"
+#include "azure_c_shared_utility/singlylinkedlist.h"
+#include "azure_uamqp_c/messaging.h"
+#include "iothub_client_private.h"
+#include "iothubtransport_amqp_messenger.h"
+#include "iothubtransport_amqp_twin_messenger.h"
+
+DEFINE_ENUM_STRINGS(TWIN_MESSENGER_SEND_STATUS, TWIN_MESSENGER_SEND_STATUS_VALUES);
+DEFINE_ENUM_STRINGS(TWIN_REPORT_STATE_RESULT, TWIN_REPORT_STATE_RESULT_VALUES);
+DEFINE_ENUM_STRINGS(TWIN_REPORT_STATE_REASON, TWIN_REPORT_STATE_REASON_VALUES);
+DEFINE_ENUM_STRINGS(TWIN_MESSENGER_STATE, TWIN_MESSENGER_STATE_VALUES);
+DEFINE_ENUM_STRINGS(TWIN_UPDATE_TYPE, TWIN_UPDATE_TYPE_VALUES);
+
+
+#define RESULT_OK 0
+#define INDEFINITE_TIME ((time_t)(-1))
+
+#define CLIENT_VERSION_PROPERTY_NAME					"com.microsoft:client-version"
+#define UNIQUE_ID_BUFFER_SIZE                           37
+
+#define EMPTY_TWIN_BODY_DATA                            ((const unsigned char*)" ")
+#define EMPTY_TWIN_BODY_SIZE                            1
+
+#define TWIN_MESSAGE_PROPERTY_OPERATION					"operation"
+#define TWIN_MESSAGE_PROPERTY_RESOURCE					"resource"
+#define TWIN_MESSAGE_PROPERTY_VERSION					"version"
+#define TWIN_MESSAGE_PROPERTY_STATUS					"status"
+
+#define TWIN_RESOURCE_DESIRED					        "/notifications/twin/properties/desired"
+#define TWIN_RESOURCE_REPORTED					        "/properties/reported"
+
+#define TWIN_CORRELATION_ID_PROPERTY_NAME				"com.microsoft:channel-correlation-id"
+#define TWIN_API_VERSION_PROPERTY_NAME					"com.microsoft:api-version"
+#define TWIN_CORRELATION_ID_PROPERTY_FORMAT				"twin:%s"
+#define TWIN_API_VERSION_NUMBER							"2016-11-14"
+
+#define DEFAULT_MAX_TWIN_SUBSCRIPTION_ERROR_COUNT		3
+#define DEFAULT_TWIN_OPERATION_TIMEOUT_SECS				300.0
+
+static char* DEFAULT_DEVICES_PATH_FORMAT =				"%s/devices/%s";
+static char* DEFAULT_TWIN_SEND_LINK_SOURCE_NAME =		"twin";
+static char* DEFAULT_TWIN_RECEIVE_LINK_TARGET_NAME =	"twin";
+
+static const char* TWIN_OPERATION_PATCH =				"PATCH";
+static const char* TWIN_OPERATION_GET =					"GET";
+static const char* TWIN_OPERATION_PUT =					"PUT";
+static const char* TWIN_OPERATION_DELETE =				"DELETE";
+
+
+#define TWIN_OPERATION_TYPE_STRINGS \
+	TWIN_OPERATION_TYPE_PATCH, \
+	TWIN_OPERATION_TYPE_GET, \
+	TWIN_OPERATION_TYPE_PUT, \
+	TWIN_OPERATION_TYPE_DELETE
+
+DEFINE_LOCAL_ENUM(TWIN_OPERATION_TYPE, TWIN_OPERATION_TYPE_STRINGS);
+
+#define TWIN_SUBSCRIPTION_STATE_STRINGS \
+	TWIN_SUBSCRIPTION_STATE_NOT_SUBSCRIBED, \
+	TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES, \
+	TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES, \
+	TWIN_SUBSCRIPTION_STATE_SUBSCRIBE_FOR_UPDATES, \
+	TWIN_SUBSCRIPTION_STATE_SUBSCRIBING, \
+	TWIN_SUBSCRIPTION_STATE_SUBSCRIBED, \
+	TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBE, \
+	TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBING
+
+DEFINE_LOCAL_ENUM(TWIN_SUBSCRIPTION_STATE, TWIN_SUBSCRIPTION_STATE_STRINGS);
+
+typedef struct TWIN_MESSENGER_INSTANCE_TAG
+{
+	char* client_version;
+	char* device_id;
+	char* iothub_host_fqdn;
+
+	TWIN_MESSENGER_STATE state;
+
+	SINGLYLINKEDLIST_HANDLE pending_patches;
+	SINGLYLINKEDLIST_HANDLE operations;
+	
+	TWIN_MESSENGER_STATE_CHANGED_CALLBACK on_state_changed_callback;
+	void* on_state_changed_context;
+
+	TWIN_SUBSCRIPTION_STATE subscription_state;
+	size_t subscription_error_count;
+	TWIN_STATE_UPDATE_CALLBACK on_message_received_callback;
+	void* on_message_received_context;
+
+	AMQP_MESSENGER_HANDLE amqp_msgr;
+	AMQP_MESSENGER_STATE amqp_msgr_state;
+	bool amqp_msgr_is_subscribed;
+} TWIN_MESSENGER_INSTANCE;
+
+typedef struct TWIN_PATCH_OPERATION_CONTEXT_TAG
+{
+	CONSTBUFFER_HANDLE data;
+	TWIN_MESSENGER_REPORT_STATE_COMPLETE_CALLBACK on_report_state_complete_callback;
+	const void* on_report_state_complete_context;
+	time_t time_enqueued;
+} TWIN_PATCH_OPERATION_CONTEXT;
+
+typedef struct TWIN_OPERATION_CONTEXT_TAG
+{
+	TWIN_OPERATION_TYPE type;
+	TWIN_MESSENGER_INSTANCE* msgr;
+	char* correlation_id;
+	TWIN_MESSENGER_REPORT_STATE_COMPLETE_CALLBACK on_report_state_complete_callback;
+	const void* on_report_state_complete_context;
+	time_t time_sent;
+} TWIN_OPERATION_CONTEXT;
+
+
+
+
+static void update_state(TWIN_MESSENGER_INSTANCE* twin_msgr, TWIN_MESSENGER_STATE new_state)
+{
+	if (new_state != twin_msgr->state)
+	{
+		TWIN_MESSENGER_STATE previous_state = twin_msgr->state;
+		twin_msgr->state = new_state;
+
+		if (twin_msgr->on_state_changed_callback != NULL)
+		{
+			twin_msgr->on_state_changed_callback(twin_msgr->on_state_changed_context, previous_state, new_state);
+		}
+	}
+}
+
+//---------- AMQP Helper Functions ----------//
+
+static int set_message_correlation_id(MESSAGE_HANDLE message, const char* value)
+{
+	int result;
+	PROPERTIES_HANDLE properties = NULL;
+
+	if (message_get_properties(message, &properties) != 0)
+	{
+		LogError("Failed getting the AMQP message properties");
+		result = __FAILURE__;
+	}
+	else if (properties == NULL && (properties = properties_create()) == NULL)
+	{
+		LogError("Failed creating properties for AMQP message");
+		result = __FAILURE__;
+	}
+	else
+	{
+		AMQP_VALUE amqp_value;
+
+		if ((amqp_value = amqpvalue_create_string(value)) == NULL)
+		{
+			LogError("Failed creating AMQP value for correlation-id");
+			result = __FAILURE__;
+		}
+		else
+		{
+			if (properties_set_correlation_id(properties, amqp_value) != RESULT_OK)
+			{
+				LogError("Failed setting the correlation id");
+				result = __FAILURE__;
+			}
+			else if (message_set_properties(message, properties) != RESULT_OK)
+			{
+				LogError("Failed setting the AMQP message properties");
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+
+			amqpvalue_destroy(amqp_value);
+		}
+
+		properties_destroy(properties);
+	}
+
+	return result;
+}
+
+static int get_message_correlation_id(MESSAGE_HANDLE message, char** correlation_id)
+{
+	int result;
+
+	PROPERTIES_HANDLE properties;
+	AMQP_VALUE amqp_value;
+
+	if (message_get_properties(message, &properties) != 0)
+	{
+		LogError("Failed getting AMQP message properties");
+		result = __FAILURE__;
+	}
+	else if (properties == NULL)
+	{
+		*correlation_id = NULL;
+		result = RESULT_OK;
+	}
+	else
+	{
+		if (properties_get_correlation_id(properties, &amqp_value) != 0 || amqp_value == NULL)
+		{
+			*correlation_id = NULL;
+			result = RESULT_OK;
+		}
+		else
+		{
+			const char* value;
+
+			if (amqpvalue_get_string(amqp_value, &value) != 0)
+			{
+				LogError("Failed retrieving string from AMQP value");
+				result = __FAILURE__;
+			}
+			else if (mallocAndStrcpy_s(correlation_id, value) != 0)
+			{
+				LogError("Failed cloning correlation-id");
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+		}
+
+		properties_destroy(properties);
+	}
+
+	return result;
+}
+
+static int add_map_item(AMQP_VALUE map, const char* name, const char* value)
+{
+	int result;
+	AMQP_VALUE amqp_value_name;
+
+	if ((amqp_value_name = amqpvalue_create_symbol(name)) == NULL)
+	{
+		LogError("Failed creating AMQP_VALUE for name");
+		result = __FAILURE__;
+	}
+	else
+	{
+		AMQP_VALUE amqp_value_value = NULL;
+		
+		if (value == NULL && (amqp_value_value = amqpvalue_create_null()) == NULL)
+		{
+			LogError("Failed creating AMQP_VALUE for NULL value");
+			result = __FAILURE__;
+		}
+		else if (value != NULL && (amqp_value_value = amqpvalue_create_string(value)) == NULL)
+		{
+			LogError("Failed creating AMQP_VALUE for value");
+			result = __FAILURE__;
+		}
+		else
+		{
+			if (amqpvalue_set_map_value(map, amqp_value_name, amqp_value_value) != 0)
+			{
+				LogError("Failed adding key/value pair to map");
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+
+			amqpvalue_destroy(amqp_value_value);
+		}
+
+		amqpvalue_destroy(amqp_value_name);
+	}
+
+	return result;
+}
+
+static int add_amqp_message_annotation(MESSAGE_HANDLE message, AMQP_VALUE msg_annotations_map)
+{
+	int result;
+	AMQP_VALUE msg_annotations;
+
+	if ((msg_annotations = amqpvalue_create_message_annotations(msg_annotations_map)) == NULL)
+	{
+		LogError("Failed creating new AMQP message annotations");
+		result = __FAILURE__;
+	}
+	else
+	{
+		if (message_set_message_annotations(message, (annotations)msg_annotations) != 0)
+		{
+			LogError("Failed setting AMQP message annotations");
+			result = __FAILURE__;
+		}
+		else
+		{
+			result = RESULT_OK;
+		}
+
+		annotations_destroy(msg_annotations);
+	}
+
+	return result;
+}
+
+
+//---------- TWIN Helpers ----------//
+
+static char* generate_unique_id()
+{
+	char* result;
+
+	if ((result = (char*)malloc(sizeof(char) * UNIQUE_ID_BUFFER_SIZE + 1)) == NULL)
+	{
+		LogError("Failed generating an unique tag (malloc failed)");
+	}
+	else
+	{
+		memset(result, 0, sizeof(char) * UNIQUE_ID_BUFFER_SIZE + 1);
+
+		if (UniqueId_Generate(result, UNIQUE_ID_BUFFER_SIZE) != UNIQUEID_OK)
+		{
+			LogError("Failed generating an unique tag (UniqueId_Generate failed)");
+			free(result);
+			result = NULL;
+		}
+	}
+
+	return result;
+}
+
+static char* generate_twin_correlation_id()
+{
+	char* result;
+	char* unique_id;
+
+	if ((unique_id = generate_unique_id()) == NULL)
+	{
+		LogError("Failed generating unique ID for correlation-id");
+		result = NULL;
+	}
+	else
+	{
+		if ((result = (char*)malloc(strlen(TWIN_CORRELATION_ID_PROPERTY_FORMAT) + strlen(unique_id) + 1)) == NULL)
+		{
+			LogError("Failed allocating correlation-id");
+			result = NULL;
+		}
+		else
+		{
+			(void)sprintf(result, TWIN_CORRELATION_ID_PROPERTY_FORMAT, unique_id);
+		}
+
+		free(unique_id);
+	}
+
+	return result;
+}
+
+static TWIN_OPERATION_CONTEXT* create_twin_operation_context(TWIN_MESSENGER_INSTANCE* twin_msgr, TWIN_OPERATION_TYPE type)
+{
+	TWIN_OPERATION_CONTEXT* result;
+
+	if ((result = (TWIN_OPERATION_CONTEXT*)malloc(sizeof(TWIN_OPERATION_CONTEXT))) == NULL)
+	{
+		LogError("Failed creating context for %s (%s)", ENUM_TO_STRING(TWIN_OPERATION_TYPE, type), twin_msgr->device_id);
+	}
+	else
+	{
+		memset(result, 0, sizeof(TWIN_OPERATION_CONTEXT));
+
+		if ((result->correlation_id = generate_unique_id()) == NULL)
+		{
+			LogError("Failed setting context correlation-id (%s, %s)", ENUM_TO_STRING(TWIN_OPERATION_TYPE, type), twin_msgr->device_id);
+			free(result);
+			result = NULL;
+		}
+		else
+		{
+			result->type = type;
+			result->msgr = twin_msgr;
+		}
+	}
+
+	return result;
+}
+
+static bool find_twin_operation_by_correlation_id(LIST_ITEM_HANDLE list_item, const void* match_context)
+{
+	TWIN_OPERATION_CONTEXT* twin_op_ctx = (TWIN_OPERATION_CONTEXT*)singlylinkedlist_item_get_value(list_item);
+	return (strcmp(twin_op_ctx->correlation_id, (const char*)match_context) == 0);
+}
+
+static bool find_twin_operation_by_type(LIST_ITEM_HANDLE list_item, const void* match_context)
+{
+	TWIN_OPERATION_CONTEXT* twin_op_ctx = (TWIN_OPERATION_CONTEXT*)singlylinkedlist_item_get_value(list_item);
+	return (twin_op_ctx->type == *(TWIN_OPERATION_TYPE*)match_context);
+}
+
+static void destroy_twin_operation_context(TWIN_OPERATION_CONTEXT* op_ctx)
+{
+	free(op_ctx->correlation_id);
+	free(op_ctx);
+}
+
+static int add_twin_operation_context_to_queue(TWIN_OPERATION_CONTEXT* twin_op_ctx)
+{
+	int result;
+
+	if (singlylinkedlist_add(twin_op_ctx->msgr->operations, (const void*)twin_op_ctx) == NULL)
+	{
+		LogError("Failed adding TWIN operation context to queue (%s, %s)", ENUM_TO_STRING(TWIN_OPERATION_TYPE, twin_op_ctx->type), twin_op_ctx->correlation_id);
+		result = __FAILURE__;
+	}
+	else
+	{
+		result = RESULT_OK;
+	}
+
+	return result;
+}
+
+static int remove_twin_operation_context_from_queue(TWIN_OPERATION_CONTEXT* twin_op_ctx)
+{
+	int result;
+	LIST_ITEM_HANDLE list_item;
+
+	if ((list_item = singlylinkedlist_find(twin_op_ctx->msgr->operations, find_twin_operation_by_correlation_id, (const void*)twin_op_ctx->correlation_id)) == NULL)
+	{
+		result = RESULT_OK;
+	}
+	else if (singlylinkedlist_remove(twin_op_ctx->msgr->operations, list_item) != 0)
+	{
+		LogError("Failed removing TWIN operation context from queue (%s, %s, %s)", 
+			twin_op_ctx->msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, twin_op_ctx->type), twin_op_ctx->correlation_id);
+		result = __FAILURE__;
+	}
+	else
+	{
+		result = RESULT_OK;
+	}
+
+	return result;
+}
+
+
+//---------- TWIN <-> AMQP Translation Functions ----------//
+
+static int parse_incoming_twin_message(MESSAGE_HANDLE message,
+	char** correlation_id,
+	bool* has_version, int64_t* version,
+	bool* has_status_code, int* status_code,
+	bool* has_twin_report, BINARY_DATA* twin_report)
+{
+	int result;
+
+	if (get_message_correlation_id(message, correlation_id) != 0)
+	{
+		LogError("Failed retrieving correlation ID from received TWIN message.");
+		result = __FAILURE__;
+	}
+	else
+	{
+		annotations message_annotations;
+
+		if (message_get_message_annotations(message, &message_annotations) != 0)
+		{
+			LogError("Failed getting TWIN message annotations");
+			result = __FAILURE__;
+		}
+		else
+		{
+			result = RESULT_OK;
+
+			if (message_annotations == NULL)
+			{
+				*has_version = false;
+				*has_status_code = false;
+			}
+			else
+			{
+				uint32_t pair_count;
+				if (amqpvalue_get_map_pair_count((AMQP_VALUE)message_annotations, &pair_count) != 0)
+				{
+					LogError("Failed getting TWIN message annotations count");
+					result = __FAILURE__;
+				}
+				else
+				{
+					uint32_t i;
+
+					*has_status_code = false;
+					*has_version = false;
+
+					for (i = 0; i < pair_count; i++)
+					{
+						AMQP_VALUE amqp_map_key;
+						AMQP_VALUE amqp_map_value;
+
+						if (amqpvalue_get_map_key_value_pair((AMQP_VALUE)message_annotations, i, &amqp_map_key, &amqp_map_value) != 0)
+						{
+							LogError("Failed getting AMQP map key/value pair (%d)", i);
+							result = __FAILURE__;
+						}
+						else
+						{
+							const char* map_key_name;
+
+							if (amqpvalue_get_symbol(amqp_map_key, &map_key_name) != 0)
+							{
+								LogError("Failed getting AMQP value symbol");
+								result = __FAILURE__;
+								break;
+							}
+							else
+							{
+								if (strcmp(TWIN_MESSAGE_PROPERTY_STATUS, map_key_name) == 0)
+								{
+									if (amqpvalue_get_type(amqp_map_value) != AMQP_TYPE_INT)
+									{
+										LogError("TWIN message status property expected to be INT");
+										result = __FAILURE__;
+										break;
+									}
+									else if (amqpvalue_get_int(amqp_map_value, status_code) != 0)
+									{
+										LogError("Failed getting TWIN message status code value");
+										result = __FAILURE__;
+										break;
+									}
+									else
+									{
+										*has_status_code = true;
+									}
+								}
+								else if (strcmp(TWIN_MESSAGE_PROPERTY_VERSION, map_key_name) == 0)
+								{
+									if (amqpvalue_get_type(amqp_map_value) != AMQP_TYPE_LONG)
+									{
+										LogError("TWIN message version property expected to be LONG");
+										result = __FAILURE__;
+										break;
+									}
+									else if (amqpvalue_get_long(amqp_map_value, version) != 0)
+									{
+										LogError("Failed getting TWIN message version value");
+										result = __FAILURE__;
+										break;
+									}
+									else
+									{
+										*has_version = true;
+									}
+								}
+								else
+								{
+									LogError("Unrecognized TWIN message property %s", map_key_name);
+								}
+
+								amqpvalue_destroy(amqp_map_value);
+							}
+
+							amqpvalue_destroy(amqp_map_key);
+						}
+					}
+				}
+
+				amqpvalue_destroy(message_annotations);
+			}
+
+			if (result == RESULT_OK)
+			{
+				MESSAGE_BODY_TYPE body_type;
+
+				if (message_get_body_type(message, &body_type) != 0)
+				{
+					LogError("Failed getting TWIN message body type");
+					result = __FAILURE__;
+				}
+				else if (body_type == MESSAGE_BODY_TYPE_DATA)
+				{
+					size_t body_count;
+
+					if (message_get_body_amqp_data_count(message, &body_count) != 0)
+					{
+						LogError("Failed getting TWIN message body count");
+						result = __FAILURE__;
+					}
+					else if (body_count != 1)
+					{
+						LogError("Unexpected number of TWIN message bodies (%d)", body_count);
+						result = __FAILURE__;
+					}
+					else if (message_get_body_amqp_data_in_place(message, 0, twin_report) != 0)
+					{
+						LogError("Failed getting TWIN message body");
+						result = __FAILURE__;
+					}
+					else
+					{
+						*has_twin_report = true;
+					}
+				}
+				else if (body_type != MESSAGE_BODY_TYPE_NONE)
+				{
+					LogError("Unexpected TWIN message body %d", body_type);
+					result = __FAILURE__;
+				}
+				else
+				{
+					*has_twin_report = false;
+				}
+			}
+		}
+
+		if (result != RESULT_OK)
+		{
+			free(*correlation_id);
+			*correlation_id = NULL;
+		}
+	}
+
+	return result;
+}
+
+static void destroy_link_attach_properties(MAP_HANDLE properties)
+{
+	Map_Destroy(properties);
+}
+
+static MAP_HANDLE create_link_attach_properties(TWIN_MESSENGER_INSTANCE* twin_msgr)
+{
+	MAP_HANDLE result;
+
+	if ((result = Map_Create(NULL)) == NULL)
+	{
+		LogError("Failed creating map for AMQP link properties (%s)", twin_msgr->device_id);
+	}
+	else
+	{
+		char* correlation_id;
+
+		if ((correlation_id = generate_twin_correlation_id()) == NULL)
+		{
+			LogError("Failed adding AMQP link property ");
+			destroy_link_attach_properties(result);
+			result = NULL;
+		}
+		else
+		{
+			if (Map_Add(result, CLIENT_VERSION_PROPERTY_NAME, twin_msgr->client_version) != MAP_OK)
+			{
+				LogError("Failed adding AMQP link property 'client version' (%s)", twin_msgr->device_id);
+				destroy_link_attach_properties(result);
+				result = NULL;
+			}
+			else if (Map_Add(result, TWIN_CORRELATION_ID_PROPERTY_NAME, correlation_id) != MAP_OK)
+			{
+				LogError("Failed adding AMQP link property 'correlation-id' (%s)", twin_msgr->device_id);
+				destroy_link_attach_properties(result);
+				result = NULL;
+			}
+			else if (Map_Add(result, TWIN_API_VERSION_PROPERTY_NAME, TWIN_API_VERSION_NUMBER) != MAP_OK)
+			{
+				LogError("Failed adding AMQP link property 'api-version' (%s)", twin_msgr->device_id);
+				destroy_link_attach_properties(result);
+				result = NULL;
+			}
+
+			free(correlation_id);
+		}
+	}
+
+	return result;
+}
+
+static const char* get_twin_operation_name(TWIN_OPERATION_TYPE op_type)
+{
+	const char* result;
+
+	switch (op_type)
+	{
+		default:
+			LogError("Unrecognized TWIN operation (%s)", ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_type));
+			result = NULL;
+			break;
+		case TWIN_OPERATION_TYPE_PATCH:
+			result = TWIN_OPERATION_PATCH;
+			break;
+		case TWIN_OPERATION_TYPE_GET:
+			result = TWIN_OPERATION_GET;
+			break;
+		case TWIN_OPERATION_TYPE_PUT:
+			result = TWIN_OPERATION_PUT;
+			break;
+		case TWIN_OPERATION_TYPE_DELETE:
+			result = TWIN_OPERATION_DELETE;
+			break;
+	}
+
+	return result;
+}
+
+static MESSAGE_HANDLE create_amqp_message_for_twin_operation(TWIN_OPERATION_TYPE op_type, char* correlation_id, CONSTBUFFER_HANDLE data)
+{
+	MESSAGE_HANDLE result;
+	const char* twin_op_name;
+
+	if ((twin_op_name = get_twin_operation_name(op_type))== NULL)
+	{
+		result = NULL;
+	}
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_063: [An `amqp_message` (MESSAGE_HANDLE) shall be created using message_create()]  
+	else if ((result = message_create()) == NULL)
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_064: [If message_create() fails, message_create_for_twin_operation shall fail and return NULL]  
+		LogError("Failed creating AMQP message (%s)", twin_op_name);
+	}
+	else
+	{
+		AMQP_VALUE msg_annotations_map;
+
+		if ((msg_annotations_map = amqpvalue_create_map()) == NULL)
+		{
+			LogError("Failed creating map for message annotations");
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+			message_destroy(result);
+			result = NULL;
+		}
+		else
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_065: [`operation=<op_type>` (GET/PATCH/PUT/DELETE) must be added to the `amqp_message` annotations]
+			if (add_map_item(msg_annotations_map, TWIN_MESSAGE_PROPERTY_OPERATION, twin_op_name) != RESULT_OK)
+			{
+				LogError("Failed adding operation to AMQP message annotations (%s)", twin_op_name);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+				message_destroy(result);
+				result = NULL;
+			}
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_066: [If `op_type` is PATCH, `resource=/properties/reported` must be added to the `amqp_message` annotations] 
+			else if ((op_type == TWIN_OPERATION_TYPE_PATCH) &&
+				add_map_item(msg_annotations_map, TWIN_MESSAGE_PROPERTY_RESOURCE, TWIN_RESOURCE_REPORTED) != RESULT_OK)
+			{
+				LogError("Failed adding resource to AMQP message annotations (%s)", twin_op_name);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+				message_destroy(result);
+				result = NULL;
+			}
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_067: [If `op_type` is PUT or DELETE, `resource=/notifications/twin/properties/desired` must be added to the `amqp_message` annotations] 
+			else if ((op_type == TWIN_OPERATION_TYPE_PUT || op_type == TWIN_OPERATION_TYPE_DELETE) &&
+				add_map_item(msg_annotations_map, TWIN_MESSAGE_PROPERTY_RESOURCE, TWIN_RESOURCE_DESIRED) != RESULT_OK)
+			{
+				LogError("Failed adding resource to AMQP message annotations (%s)", twin_op_name);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+				message_destroy(result);
+				result = NULL;
+			}
+			else if (add_amqp_message_annotation(result, msg_annotations_map) != RESULT_OK)
+			{
+				LogError("Failed adding annotations to AMQP message (%s)", twin_op_name);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+				message_destroy(result);
+				result = NULL;
+			}
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_068: [The `correlation-id` property of `amqp_message` shall be set with an UUID string]  
+			else if (set_message_correlation_id(result, correlation_id) != RESULT_OK)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_069: [If setting `correlation-id` fails, message_create_for_twin_operation shall fail and return NULL]  
+				LogError("Failed AMQP message correlation-id (%s)", twin_op_name);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+				message_destroy(result);
+				result = NULL;
+			}
+			else
+			{
+				BINARY_DATA binary_data;
+
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_070: [If `data` is not NULL, it shall be added to `amqp_message` using message_add_body_amqp_data()]  
+				if (data != NULL)
+				{
+					const CONSTBUFFER* data_buffer;
+					data_buffer = CONSTBUFFER_GetContent(data);
+					binary_data.bytes = data_buffer->buffer;
+					binary_data.length = data_buffer->size;
+				}
+				else
+				{
+					binary_data.bytes = EMPTY_TWIN_BODY_DATA;
+					binary_data.length = EMPTY_TWIN_BODY_SIZE;
+				}
+
+				if (message_add_body_amqp_data(result, binary_data) != 0)
+				{
+					LogError("Failed adding twin patch data to AMQP message body");
+					// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_072: [If any errors occur, message_create_for_twin_operation shall release all memory it has allocated]  
+					message_destroy(result);
+					// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_071: [If message_add_body_amqp_data() fails, message_create_for_twin_operation shall fail and return NULL]  
+					result = NULL;
+				}
+			}
+
+			amqpvalue_destroy(msg_annotations_map);
+		}
+	}
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_073: [If no errors occur, message_create_for_twin_operation shall return `amqp_message`]  
+	return result;
+}
+
+static TWIN_REPORT_STATE_RESULT get_twin_messenger_result_from(AMQP_MESSENGER_SEND_RESULT amqp_send_result)
+{
+	TWIN_REPORT_STATE_RESULT result;
+
+	switch (amqp_send_result)
+	{
+		case AMQP_MESSENGER_SEND_RESULT_SUCCESS:
+			result = TWIN_REPORT_STATE_RESULT_SUCCESS;
+			break;
+		case AMQP_MESSENGER_SEND_RESULT_CANCELLED:
+			result = TWIN_REPORT_STATE_RESULT_CANCELLED;
+			break;
+		case AMQP_MESSENGER_SEND_RESULT_ERROR:
+			result = TWIN_REPORT_STATE_RESULT_ERROR;
+			break;
+		default:
+			LogError("Unrecognized enum value %s", ENUM_TO_STRING(AMQP_MESSENGER_SEND_RESULT, amqp_send_result));
+			result = TWIN_REPORT_STATE_RESULT_ERROR;
+			break;
+	};
+
+	return result;
+}
+
+static TWIN_REPORT_STATE_REASON get_twin_messenger_reason_from(AMQP_MESSENGER_REASON amqp_reason)
+{
+	TWIN_REPORT_STATE_REASON result;
+
+	switch (amqp_reason)
+	{
+		case AMQP_MESSENGER_REASON_NONE:
+			result = TWIN_REPORT_STATE_REASON_NONE;
+			break;
+		case AMQP_MESSENGER_REASON_FAIL_SENDING:
+			result = TWIN_REPORT_STATE_REASON_FAIL_SENDING;
+			break;
+		case AMQP_MESSENGER_REASON_TIMEOUT:
+			result = TWIN_REPORT_STATE_REASON_TIMEOUT;
+			break;
+		case AMQP_MESSENGER_REASON_MESSENGER_DESTROYED:
+			result = TWIN_REPORT_STATE_REASON_MESSENGER_DESTROYED;
+			break;
+		case AMQP_MESSENGER_REASON_CANNOT_PARSE:
+			result = TWIN_REPORT_STATE_REASON_NONE;
+			break;
+		default:
+			LogError("Unrecognized enum value %s (%d)", ENUM_TO_STRING(AMQP_MESSENGER_REASON, amqp_reason), amqp_reason);
+			result = TWIN_REPORT_STATE_REASON_NONE;
+			break;
+	};
+
+	return result;
+}
+
+static void on_amqp_send_complete_callback(AMQP_MESSENGER_SEND_RESULT result, AMQP_MESSENGER_REASON reason, void* context)
+{
+	// Applicable to TWIN requests for reported state PATCH, GET, PUT, DELETE.
+
+	if (context == NULL)
+	{
+		LogError("Invalid argument (context is NULL)");
+	}
+	else
+	{
+		TWIN_OPERATION_CONTEXT* twin_op_ctx = (TWIN_OPERATION_CONTEXT*)context;
+
+		if (result != AMQP_MESSENGER_SEND_RESULT_SUCCESS)
+		{
+			if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PATCH)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_095: [If operation is a reported state PATCH, if a failure occurs `on_report_state_complete_callback` shall be invoked with TWIN_REPORT_STATE_RESULT_ERROR, status code from the AMQP response and the saved context]  
+				if (twin_op_ctx->on_report_state_complete_callback != NULL)
+				{
+					TWIN_REPORT_STATE_RESULT callback_result;
+					TWIN_REPORT_STATE_REASON callback_reason;
+
+					callback_result = get_twin_messenger_result_from(result);
+					callback_reason = get_twin_messenger_reason_from(reason);
+
+					twin_op_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_NONE, 0, (void*)twin_op_ctx->on_report_state_complete_context);
+				}
+			}
+			else if (reason != AMQP_MESSENGER_REASON_MESSENGER_DESTROYED)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_096: [If operation is a GET/PUT/DELETE, if a failure occurs the TWIN messenger shall attempt to subscribe/unsubscribe again]  
+				LogError("Failed sending TWIN operation request (%s, %s, %s, %s, %s)",
+					twin_op_ctx->msgr->device_id, 
+					ENUM_TO_STRING(TWIN_OPERATION_TYPE, twin_op_ctx->type),
+					twin_op_ctx->correlation_id, 
+					ENUM_TO_STRING(AMQP_MESSENGER_SEND_RESULT, result), ENUM_TO_STRING(AMQP_MESSENGER_REASON, reason));
+
+				if (twin_op_ctx->type == TWIN_OPERATION_TYPE_GET &&
+					twin_op_ctx->msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES)
+				{
+					twin_op_ctx->msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES;
+					twin_op_ctx->msgr->subscription_error_count++;
+				}
+				else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PUT &&
+					twin_op_ctx->msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES)
+				{
+					twin_op_ctx->msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES;
+					twin_op_ctx->msgr->subscription_error_count++;
+				}
+			}
+
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_097: [If a failure occurred, the current operation shall be removed from `twin_msgr->operations`]  
+			if (remove_twin_operation_context_from_queue(twin_op_ctx) != RESULT_OK)
+			{
+				update_state(twin_op_ctx->msgr, TWIN_MESSENGER_STATE_ERROR);
+			}
+			else
+			{
+				destroy_twin_operation_context(twin_op_ctx);
+			}
+		}
+	}
+}
+
+static int send_twin_operation_request(TWIN_MESSENGER_INSTANCE* twin_msgr, TWIN_OPERATION_CONTEXT* op_ctx, CONSTBUFFER_HANDLE data)
+{
+	int result;
+	MESSAGE_HANDLE amqp_message;
+
+	if ((amqp_message = create_amqp_message_for_twin_operation(op_ctx->type, op_ctx->correlation_id, data)) == NULL)
+	{
+		LogError("Failed creating request message (%s, %s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_ctx->type), op_ctx->correlation_id);
+		result = __FAILURE__;
+	}
+	else
+	{
+		if ((op_ctx->time_sent = get_time(NULL)) == INDEFINITE_TIME)
+		{
+			LogError("Failed setting TWIN operation sent time (%s, %s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_ctx->type), op_ctx->correlation_id);
+			result = __FAILURE__;
+		}
+		else if (amqp_messenger_send_async(twin_msgr->amqp_msgr, amqp_message, on_amqp_send_complete_callback, (void*)op_ctx) != 0)
+		{
+			LogError("Failed sending request message for (%s, %s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_ctx->type), op_ctx->correlation_id);
+			result = __FAILURE__;
+		}
+		else
+		{
+			result = RESULT_OK;
+		}
+
+		message_destroy(amqp_message);
+	}
+
+	return result;
+}
+
+
+//---------- Internal Helpers----------//
+
+static bool remove_expired_twin_patch_request(const void* item, const void* match_context, bool* continue_processing)
+{
+	bool remove_item;
+
+	if (item == NULL || match_context == NULL || continue_processing == NULL)
+	{
+		LogError("Invalid argument (item=%p, match_context=%p, continue_processing=%p)", item, match_context, continue_processing);
+		*continue_processing = false;
+		remove_item = false;
+	}
+	else
+	{
+
+		time_t current_time = *(time_t*)match_context;
+		TWIN_PATCH_OPERATION_CONTEXT* twin_patch_ctx = (TWIN_PATCH_OPERATION_CONTEXT*)item;
+
+		if (get_difftime(current_time, twin_patch_ctx->time_enqueued) >= DEFAULT_TWIN_OPERATION_TIMEOUT_SECS)
+		{
+			remove_item = true;
+			*continue_processing = true;
+
+			if (twin_patch_ctx->on_report_state_complete_callback != NULL)
+			{
+				twin_patch_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_TIMEOUT, 0, twin_patch_ctx->on_report_state_complete_context);
+			}
+
+			CONSTBUFFER_Destroy(twin_patch_ctx->data);
+			free(twin_patch_ctx);
+		}
+		else
+		{
+			remove_item = false;
+			*continue_processing = false;
+		}
+	}
+
+	return remove_item;
+}
+
+static bool remove_expired_twin_operation_request(const void* item, const void* match_context, bool* continue_processing)
+{
+	bool result;
+
+	if (item == NULL || match_context == NULL || continue_processing == NULL)
+	{
+		LogError("Invalid argument (item=%p, match_context=%p, continue_processing=%p)", item, match_context, continue_processing);
+		*continue_processing = false;
+		result = false;
+	}
+	else
+	{
+		TWIN_OPERATION_CONTEXT* twin_op_ctx = (TWIN_OPERATION_CONTEXT*)item;
+		TWIN_MESSENGER_INSTANCE* twin_msgr = twin_op_ctx->msgr;
+		time_t current_time = *(time_t*)match_context;
+
+		if (get_difftime(current_time, twin_op_ctx->time_sent) < DEFAULT_TWIN_OPERATION_TIMEOUT_SECS)
+		{
+			result = false;
+			// All next elements in the list have a later time_sent, so they won't be expired, and don't need to be removed.
+			*continue_processing = false;
+		}
+		else
+		{
+			LogError("Twin operation timed out (%s, %s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, twin_op_ctx->type), twin_op_ctx->correlation_id);
+			result = true;
+			*continue_processing = true;
+
+			if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PATCH)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_081: [If a timed-out item is a reported property PATCH, `on_report_state_complete_callback` shall be invoked with RESULT_ERROR and REASON_TIMEOUT]  
+				if (twin_op_ctx->on_report_state_complete_callback != NULL)
+				{
+					twin_op_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_TIMEOUT, 0, twin_op_ctx->on_report_state_complete_context);
+				}
+			}
+			else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_GET)
+			{
+				if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES)
+				{
+					twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES;
+					twin_msgr->subscription_error_count++;
+				}
+			}
+			else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PUT)
+			{
+				if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_SUBSCRIBING)
+				{
+					twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_SUBSCRIBE_FOR_UPDATES;
+					twin_msgr->subscription_error_count++;
+				}
+			}
+			else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_DELETE)
+			{
+				if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBING)
+				{
+					twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBE;
+					twin_msgr->subscription_error_count++;
+				}
+			}
+
+			destroy_twin_operation_context(twin_op_ctx);
+		}
+	}
+
+	return result;
+}
+
+static void process_timeouts(TWIN_MESSENGER_INSTANCE* twin_msgr)
+{
+	time_t current_time;
+
+	if ((current_time = get_time(NULL)) == INDEFINITE_TIME)
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_082: [If any failure occurs while verifying/removing timed-out items `twin_msgr->state` shall be set to TWIN_MESSENGER_STATE_ERROR and user informed]  
+		LogError("Failed obtaining current time (%s)", twin_msgr->device_id);
+		update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+	}
+	else
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_080: [twin_messenger_do_work() shall remove and destroy any timed out items from `twin_msgr->pending_patches` and `twin_msgr->operations`]  
+		(void)singlylinkedlist_remove_if(twin_msgr->pending_patches, remove_expired_twin_patch_request, (const void*)&current_time);
+		(void)singlylinkedlist_remove_if(twin_msgr->operations, remove_expired_twin_operation_request, (const void*)&current_time);
+	}
+}
+
+static bool send_pending_twin_patch(const void* item, const void* match_context, bool* continue_processing)
+{
+	bool result;
+
+	if (item == NULL || match_context == NULL || continue_processing == NULL)
+	{
+		LogError("Invalid argument (item=%p, match_context=%p, continue_processing=%p)", item, match_context, continue_processing);
+		*continue_processing = false;
+		result = false;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)match_context;
+		TWIN_PATCH_OPERATION_CONTEXT* twin_patch_ctx = (TWIN_PATCH_OPERATION_CONTEXT*)item;
+		TWIN_OPERATION_CONTEXT* twin_op_ctx;
+
+		if ((twin_op_ctx = create_twin_operation_context(twin_msgr, TWIN_OPERATION_TYPE_PATCH)) == NULL)
+		{
+			LogError("Failed creating context for sending reported state (%s)", twin_msgr->device_id);
+
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_061: [If any other failure occurs sending the PATCH request, `on_report_state_complete_callback` shall be invoked with RESULT_ERROR and REASON_INTERNAL_ERROR]
+			if (twin_patch_ctx->on_report_state_complete_callback != NULL)
+			{
+				twin_patch_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_INTERNAL_ERROR, 0, twin_patch_ctx->on_report_state_complete_context);
+			}
+		}
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_062: [If amqp_send_async() succeeds, the PATCH request shall be queued into `twin_msgr->operations`]
+		else if (add_twin_operation_context_to_queue(twin_op_ctx) != RESULT_OK)
+		{
+			LogError("Failed adding TWIN operation context to queue (%s)", twin_msgr->device_id);
+
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_061: [If any other failure occurs sending the PATCH request, `on_report_state_complete_callback` shall be invoked with RESULT_ERROR and REASON_INTERNAL_ERROR]
+			if (twin_patch_ctx->on_report_state_complete_callback != NULL)
+			{
+				twin_patch_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_INTERNAL_ERROR, 0, twin_patch_ctx->on_report_state_complete_context);
+			}
+
+			destroy_twin_operation_context(twin_op_ctx);
+		}
+		else
+		{
+			twin_op_ctx->on_report_state_complete_callback = twin_patch_ctx->on_report_state_complete_callback;
+			twin_op_ctx->on_report_state_complete_context = twin_patch_ctx->on_report_state_complete_context;
+
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_059: [If reported property PATCH shall be sent as an uAMQP MESSAGE_HANDLE instance using amqp_send_async() passing `on_amqp_send_complete_callback`]
+			if (send_twin_operation_request(twin_msgr, twin_op_ctx, twin_patch_ctx->data) != RESULT_OK)
+			{
+				LogError("Failed sending reported state (%s)", twin_msgr->device_id);
+
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_060: [If amqp_send_async() fails, `on_report_state_complete_callback` shall be invoked with RESULT_ERROR and REASON_FAIL_SENDING]
+				if (twin_patch_ctx->on_report_state_complete_callback != NULL)
+				{
+					twin_patch_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_FAIL_SENDING, 0, twin_patch_ctx->on_report_state_complete_context);
+				}
+
+				(void)remove_twin_operation_context_from_queue(twin_op_ctx);
+				destroy_twin_operation_context(twin_op_ctx);
+			}
+		}
+
+		CONSTBUFFER_Destroy(twin_patch_ctx->data);
+		free(twin_patch_ctx);
+
+		*continue_processing = true;
+		result = true;
+	}
+
+	return result;
+}
+
+static void process_twin_subscription(TWIN_MESSENGER_INSTANCE* twin_msgr)
+{
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_078: [If failures occur sending subscription requests to the service for more than 3 times, TWIN messenger shall set its state to TWIN_MESSENGER_STATE_ERROR and inform the user]
+	if (twin_msgr->subscription_error_count >= DEFAULT_MAX_TWIN_SUBSCRIPTION_ERROR_COUNT)
+	{
+		LogError("Maximum number of TWIN subscription-related failures reached (%s, %d)", twin_msgr->device_id, twin_msgr->subscription_error_count);
+		update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+	}
+	else
+	{
+		TWIN_OPERATION_TYPE op_type = TWIN_OPERATION_TYPE_PATCH;
+		TWIN_SUBSCRIPTION_STATE next_subscription_state = twin_msgr->subscription_state;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_074: [If subscribing, twin_messenger_do_work() shall request a complete desired properties report]
+		if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES)
+		{
+			op_type = TWIN_OPERATION_TYPE_GET;
+			next_subscription_state = TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES;
+		}
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_075: [If a complete desired report has been received, the TWIN messenger shall request partial updates to desired properties]
+		else if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_SUBSCRIBE_FOR_UPDATES)
+		{
+			op_type = TWIN_OPERATION_TYPE_PUT;
+			next_subscription_state = TWIN_SUBSCRIPTION_STATE_SUBSCRIBING;
+		}
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_076: [If unsubscribing, twin_messenger_do_work() shall send a DELETE request to the service]
+		else if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBE)
+		{
+			op_type = TWIN_OPERATION_TYPE_PUT;
+			next_subscription_state = TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBING;
+		}
+
+		if (next_subscription_state != twin_msgr->subscription_state)
+		{
+			TWIN_OPERATION_CONTEXT* twin_op_ctx;
+
+			if ((twin_op_ctx = create_twin_operation_context(twin_msgr, op_type)) == NULL)
+			{
+				LogError("Failed creating a context for TWIN request (%s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_type));
+				update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+			}
+			else
+			{
+				if (add_twin_operation_context_to_queue(twin_op_ctx) != RESULT_OK)
+				{
+					LogError("Failed queueing TWIN request context (%s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_type));
+					destroy_twin_operation_context(twin_op_ctx);
+					update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+				}
+				else if (send_twin_operation_request(twin_msgr, twin_op_ctx, NULL) != RESULT_OK)
+				{
+					LogError("Failed sending TWIN request (%s, %s)", twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, op_type));
+
+					(void)remove_twin_operation_context_from_queue(twin_op_ctx);
+					destroy_twin_operation_context(twin_op_ctx);
+					update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+				}
+				else
+				{
+					twin_msgr->subscription_state = next_subscription_state;
+				}
+			}
+		}
+	}
+}
+
+static bool cancel_all_pending_twin_operations(const void* item, const void* match_context, bool* continue_processing)
+{
+	bool result;
+
+	if (item == NULL || continue_processing == NULL)
+	{
+		LogError("Invalid argument (item=%p, continue_processing=%p)", item, continue_processing);
+		*continue_processing = false;
+		result = false;
+	}
+	else
+	{
+		TWIN_OPERATION_CONTEXT* twin_op_ctx = (TWIN_OPERATION_CONTEXT*)item;
+		(void)match_context;
+
+		if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PATCH)
+		{
+			if (twin_op_ctx->on_report_state_complete_callback != NULL)
+			{
+				twin_op_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_CANCELLED, TWIN_REPORT_STATE_REASON_MESSENGER_DESTROYED, 0, twin_op_ctx->on_report_state_complete_context);
+			}
+		}
+
+		destroy_twin_operation_context(twin_op_ctx);
+
+		*continue_processing = true;
+		result = true;
+	}
+
+	return result;
+}
+
+static bool cancel_pending_twin_patch_operation(const void* item, const void* match_context, bool* continue_processing)
+{
+	bool result;
+
+	if (item == NULL)
+	{
+		LogError("Invalid argument (item is NULL)");
+		*continue_processing = false;
+		result = false;
+	}
+	else
+	{
+		TWIN_PATCH_OPERATION_CONTEXT* twin_patch_ctx = (TWIN_PATCH_OPERATION_CONTEXT*)item;
+		(void)match_context;
+
+		if (twin_patch_ctx->on_report_state_complete_callback != NULL)
+		{
+			twin_patch_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_CANCELLED, TWIN_REPORT_STATE_REASON_MESSENGER_DESTROYED, 0, twin_patch_ctx->on_report_state_complete_context);
+		}
+
+		CONSTBUFFER_Destroy(twin_patch_ctx->data);
+		free(twin_patch_ctx);
+
+		*continue_processing = true;
+		result = true;
+	}
+
+	return result;
+}
+
+static void internal_twin_messenger_destroy(TWIN_MESSENGER_INSTANCE* twin_msgr)
+{
+	if (twin_msgr->amqp_msgr != NULL)
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_099: [`twin_msgr->amqp_messenger` shall be destroyed using amqp_messenger_destroy()]  
+		amqp_messenger_destroy(twin_msgr->amqp_msgr);
+	}
+
+	if (twin_msgr->pending_patches != NULL)
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_100: [All elements of `twin_msgr->pending_patches` shall be removed, invoking `on_report_state_complete_callback` for each with TWIN_REPORT_STATE_REASON_MESSENGER_DESTROYED]  
+		if (singlylinkedlist_remove_if(twin_msgr->pending_patches, cancel_pending_twin_patch_operation, twin_msgr) != 0)
+		{
+			LogError("Failed removing pending desired properties PATCH operation (%s)", twin_msgr->device_id);
+		}
+
+		singlylinkedlist_destroy(twin_msgr->pending_patches);
+	}
+
+	if (twin_msgr->operations != NULL)
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_101: [All elements of `twin_msgr->operations` shall be removed, invoking `on_report_state_complete_callback` for each PATCH with TWIN_REPORT_STATE_REASON_MESSENGER_DESTROYED]  
+		singlylinkedlist_remove_if(twin_msgr->operations, cancel_all_pending_twin_operations, (const void*)twin_msgr);
+		singlylinkedlist_destroy(twin_msgr->operations);
+	}
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_102: [twin_messenger_destroy() shall release all memory allocated for and within `twin_msgr`]  
+	if (twin_msgr->client_version != NULL)
+	{
+		free(twin_msgr->client_version);
+	}
+
+	if (twin_msgr->device_id != NULL)
+	{
+		free(twin_msgr->device_id);
+	}
+
+	if (twin_msgr->iothub_host_fqdn != NULL)
+	{
+		free(twin_msgr->iothub_host_fqdn);
+	}
+
+	free(twin_msgr);
+}
+
+
+//---------- Internal Callbacks ----------//
+
+static AMQP_MESSENGER_DISPOSITION_RESULT on_amqp_message_received_callback(MESSAGE_HANDLE message, AMQP_MESSENGER_MESSAGE_DISPOSITION_INFO* disposition_info, void* context)
+{
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_084: [If `message` or `context` are NULL, on_amqp_message_received_callback shall return immediately]  
+	AMQP_MESSENGER_DISPOSITION_RESULT disposition_result;
+
+	if (message == NULL || context == NULL)
+	{
+		LogError("Invalid argument (message=%p, context=%p)", message, context);
+		disposition_result = AMQP_MESSENGER_DISPOSITION_RESULT_REJECTED;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)context;
+
+		char* correlation_id;
+
+		bool has_status_code;
+		int status_code;
+		
+		bool has_version;
+		int64_t version;
+		
+		bool has_twin_report;
+		BINARY_DATA twin_report;
+
+		amqp_messenger_destroy_disposition_info(disposition_info);
+		disposition_result = AMQP_MESSENGER_DISPOSITION_RESULT_ACCEPTED;
+
+		if (parse_incoming_twin_message(message, &correlation_id, &has_version, &version, &has_status_code, &status_code, &has_twin_report, &twin_report) != 0)
+		{
+			LogError("Failed parsing incoming TWIN message (%s)", twin_msgr->device_id);
+		}
+		else
+		{
+			if (correlation_id != NULL)
+			{
+				// It is supposed to be a request sent previously (reported properties PATCH, GET, PUT or DELETE).
+
+				LIST_ITEM_HANDLE list_item;
+				if ((list_item = singlylinkedlist_find(twin_msgr->operations, find_twin_operation_by_correlation_id, (const void*)correlation_id)) == NULL)
+				{
+					LogError("Could not find context of TWIN incoming message (%s, %s)", twin_msgr->device_id, correlation_id);
+				}
+				else
+				{
+					TWIN_OPERATION_CONTEXT* twin_op_ctx;
+
+					if ((twin_op_ctx = (TWIN_OPERATION_CONTEXT*)singlylinkedlist_item_get_value(list_item)) == NULL)
+					{
+						LogError("Could not get context for incoming TWIN message (%s, %s)", twin_msgr->device_id, correlation_id);
+					}
+					else
+					{	
+						if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PATCH)
+						{							
+							if (!has_status_code)
+							{
+								// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_086: [If `message` is a failed response for a PATCH request, the `on_report_state_complete_callback` shall be invoked if provided passing RESULT_ERROR and the status_code zero]  
+								LogError("Received an incoming TWIN message for a PATCH operation, but with no status code (%s, %s)", twin_msgr->device_id, correlation_id);
+
+								disposition_result = AMQP_MESSENGER_DISPOSITION_RESULT_REJECTED;
+								
+								if (twin_op_ctx->on_report_state_complete_callback != NULL)
+								{
+									twin_op_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_ERROR, TWIN_REPORT_STATE_REASON_INVALID_RESPONSE, 0, twin_op_ctx->on_report_state_complete_context);
+								}
+							}
+							else
+							{
+								// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_085: [If `message` is a success response for a PATCH request, the `on_report_state_complete_callback` shall be invoked if provided passing RESULT_SUCCESS and the status_code received]  
+								if (twin_op_ctx->on_report_state_complete_callback != NULL)
+								{
+									twin_op_ctx->on_report_state_complete_callback(TWIN_REPORT_STATE_RESULT_SUCCESS, TWIN_REPORT_STATE_REASON_NONE, status_code, twin_op_ctx->on_report_state_complete_context);
+								}
+							}
+						}
+						else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_GET)
+						{
+							if (!has_twin_report)
+							{
+								// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_089: [If `message` is a failed response for a GET request, the TWIN messenger shall attempt to send another GET request]  
+								LogError("Received an incoming TWIN message for a GET operation, but with no report (%s, %s)", twin_msgr->device_id, correlation_id);
+
+								disposition_result = AMQP_MESSENGER_DISPOSITION_RESULT_REJECTED;
+
+								if (twin_op_ctx->msgr->on_message_received_callback != NULL)
+								{
+									twin_op_ctx->msgr->on_message_received_callback(TWIN_UPDATE_TYPE_COMPLETE, NULL, 0, twin_op_ctx->msgr->on_message_received_context);
+								}
+
+								if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES)
+								{
+									twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES;
+									twin_msgr->subscription_error_count++;
+								}
+							}
+							else
+							{
+								// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_087: [If `message` is a success response for a GET request, `on_message_received_callback` shall be invoked with TWIN_UPDATE_TYPE_COMPLETE and the message body received]  
+								if (twin_op_ctx->msgr->on_message_received_callback != NULL)
+								{
+									twin_op_ctx->msgr->on_message_received_callback(TWIN_UPDATE_TYPE_COMPLETE, (const char*)twin_report.bytes, twin_report.length, twin_op_ctx->msgr->on_message_received_context);
+								}
+
+								// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_088: [If `message` is a success response for a GET request, the TWIN messenger shall trigger the subscription for partial updates]  
+								if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_GETTING_COMPLETE_PROPERTIES)
+								{
+									twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_SUBSCRIBE_FOR_UPDATES;
+									twin_msgr->subscription_error_count = 0;
+								}
+							}
+						}
+						else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_PUT)
+						{
+							if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_SUBSCRIBED)
+							{
+								bool subscription_succeeded = true;
+
+								if (!has_status_code)
+								{
+									LogError("Received an incoming TWIN message for a PUT operation, but with no status code (%s, %s)", twin_msgr->device_id, correlation_id);
+									
+									subscription_succeeded = false;
+								}
+								else if (status_code < 200 || status_code >= 300)
+								{
+									LogError("Received status code %d for TWIN subscription request (%s, %s)", status_code, twin_msgr->device_id, correlation_id);
+									
+									subscription_succeeded = false;
+								}
+
+								if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_SUBSCRIBING)
+								{
+									if (subscription_succeeded)
+									{
+										twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_SUBSCRIBED;
+										twin_msgr->subscription_error_count = 0;
+									}
+									else
+									{
+										// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_090: [If `message` is a failed response for a PUT request, the TWIN messenger shall attempt to send another PUT request]  
+										twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_SUBSCRIBE_FOR_UPDATES;
+										twin_msgr->subscription_error_count++;
+									}
+								}
+							}
+						}
+						else if (twin_op_ctx->type == TWIN_OPERATION_TYPE_DELETE)
+						{
+							if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_NOT_SUBSCRIBED)
+							{
+								bool unsubscription_succeeded = true;
+
+								if (!has_status_code)
+								{
+									LogError("Received an incoming TWIN message for a DELETE operation, but with no status code (%s, %s)", twin_msgr->device_id, correlation_id);
+									
+									unsubscription_succeeded = false;
+								}
+								else if (status_code < 200 || status_code >= 300)
+								{
+									LogError("Received status code %d for TWIN unsubscription request (%s, %s)", status_code, twin_msgr->device_id, correlation_id);
+									
+									unsubscription_succeeded = false;
+								}
+
+								if (twin_msgr->subscription_state == TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBING)
+								{
+									if (unsubscription_succeeded)
+									{
+										twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_NOT_SUBSCRIBED;
+										twin_msgr->subscription_error_count = 0;
+									}
+									else
+									{
+										// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_091: [If `message` is a failed response for a DELETE request, the TWIN messenger shall attempt to send another DELETE request]  
+										twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBE;
+										twin_msgr->subscription_error_count++;
+									}
+								}
+							}
+						}
+
+						destroy_twin_operation_context(twin_op_ctx);
+					}
+
+					// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_092: [The corresponding TWIN request shall be removed from `twin_msgr->operations` and destroyed]  
+					if (singlylinkedlist_remove(twin_msgr->operations, list_item) != 0)
+					{
+						// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_093: [The corresponding TWIN request failed to be removed from `twin_msgr->operations`, `twin_msgr->state` shall be set to TWIN_MESSENGER_STATE_ERROR and informed to the user]  
+						LogError("Failed removing context for incoming TWIN message (%s, %s, %s)",
+							twin_msgr->device_id, ENUM_TO_STRING(TWIN_OPERATION_TYPE, twin_op_ctx->type), correlation_id);
+						
+						update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+					}
+				}
+
+				free(correlation_id);
+			}
+			else if (has_twin_report)
+			{
+				// It is supposed to be a desired properties delta update.
+
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_094: [If `message` is not a client request, `on_message_received_callback` shall be invoked with TWIN_UPDATE_TYPE_PARTIAL and the message body received]  
+				if (twin_msgr->on_message_received_callback != NULL)
+				{
+					twin_msgr->on_message_received_callback(TWIN_UPDATE_TYPE_PARTIAL, (const char*)twin_report.bytes, twin_report.length, twin_msgr->on_message_received_context);
+				}
+			}
+			else
+			{
+				LogError("Received TWIN message with no correlation-id and no report (%s)", twin_msgr->device_id);
+			}
+		}
+	}
+
+	return disposition_result;
+}
+
+static TWIN_MESSENGER_STATE get_twin_state_from(AMQP_MESSENGER_STATE amqp_messenger_state)
+{
+	TWIN_MESSENGER_STATE result;
+
+	switch (amqp_messenger_state)
+	{
+		case AMQP_MESSENGER_STATE_STOPPED:
+			result = TWIN_MESSENGER_STATE_STOPPED;
+			break;
+		case AMQP_MESSENGER_STATE_STOPPING:
+			result = TWIN_MESSENGER_STATE_STOPPING;
+			break;
+		case AMQP_MESSENGER_STATE_STARTED:
+			result = TWIN_MESSENGER_STATE_STARTED;
+			break;
+		case AMQP_MESSENGER_STATE_STARTING:
+			result = TWIN_MESSENGER_STATE_STARTING;
+			break;
+		case AMQP_MESSENGER_STATE_ERROR:
+		default:
+			result = TWIN_MESSENGER_STATE_ERROR;
+			break;
+	};
+
+	return result;
+}
+
+static void on_amqp_messenger_state_changed_callback(void* context, AMQP_MESSENGER_STATE previous_state, AMQP_MESSENGER_STATE new_state)
+{
+	if (context == NULL)
+	{
+		LogError("Invalid argument (context is NULL)");
+	}
+	else if (new_state != previous_state)
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)context;
+
+		if (twin_msgr->state == TWIN_MESSENGER_STATE_STARTING && new_state == AMQP_MESSENGER_STATE_STARTED)
+		{
+			if (twin_msgr->amqp_msgr_is_subscribed)
+			{
+				update_state(twin_msgr, TWIN_MESSENGER_STATE_STARTED);
+			}
+			// Else, it shall wait for the moment the AMQP msgr is subscribed.
+		}
+		else if (twin_msgr->state == TWIN_MESSENGER_STATE_STOPPING && new_state == TWIN_MESSENGER_STATE_STOPPED)
+		{
+			if (!twin_msgr->amqp_msgr_is_subscribed)
+			{
+				update_state(twin_msgr, TWIN_MESSENGER_STATE_STOPPED);
+			}
+			// Else, it shall wait for the moment the AMQP msgr is unsubscribed.
+		}
+		else if ((twin_msgr->state == TWIN_MESSENGER_STATE_STARTING && new_state == AMQP_MESSENGER_STATE_STARTING) ||
+				(twin_msgr->state == TWIN_MESSENGER_STATE_STOPPING && new_state == AMQP_MESSENGER_STATE_STOPPING))
+		{
+			// Do nothing, this is expected.
+		}
+		else
+		{
+			LogError("Unexpected AMQP messenger state (%s, %s, %s)", 
+				twin_msgr->device_id, ENUM_TO_STRING(TWIN_MESSENGER_STATE, twin_msgr->state), ENUM_TO_STRING(AMQP_MESSENGER_STATE, new_state));
+			
+			update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+		}
+
+		twin_msgr->amqp_msgr_state = new_state;
+	}
+}
+
+static void on_amqp_messenger_subscription_changed_callback(void* context, bool is_subscribed)
+{
+	if (context == NULL)
+	{
+		LogError("Invalid argument (context is NULL)");
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)context;
+
+		if (twin_msgr->state == TWIN_MESSENGER_STATE_STARTING && is_subscribed)
+		{
+			if (twin_msgr->amqp_msgr_state == AMQP_MESSENGER_STATE_STARTED)
+			{
+				update_state(twin_msgr, TWIN_MESSENGER_STATE_STARTED);
+			}
+			// Else, it shall wait for the moment the AMQP msgr is STARTED.
+		}
+		else if (twin_msgr->state == TWIN_MESSENGER_STATE_STOPPING && !is_subscribed)
+		{
+			if (twin_msgr->amqp_msgr_state == AMQP_MESSENGER_STATE_STOPPED)
+			{
+				update_state(twin_msgr, TWIN_MESSENGER_STATE_STOPPED);
+			}
+			// Else, it shall wait for the moment the AMQP msgr is STOPPED.
+		}
+		else
+		{
+			LogError("Unexpected AMQP messenger state (%s, %s, %d)",
+				twin_msgr->device_id, ENUM_TO_STRING(TWIN_MESSENGER_STATE, twin_msgr->state), is_subscribed);
+
+			update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+		}
+
+		twin_msgr->amqp_msgr_is_subscribed = is_subscribed;
+	}
+}
+
+
+//---------- Public APIs ----------//
+
+TWIN_MESSENGER_HANDLE twin_messenger_create(const TWIN_MESSENGER_CONFIG* messenger_config)
+{
+	TWIN_MESSENGER_INSTANCE* twin_msgr;
+	
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_001: [If parameter `messenger_config` is NULL, twin_messenger_create() shall return NULL]  
+	if (messenger_config == NULL)
+	{
+		LogError("Invalid argument (messenger_config is NULL)");
+		twin_msgr = NULL;
+	}
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_002: [If `messenger_config`'s `device_id`, `iothub_host_fqdn` or `client_version` is NULL, twin_messenger_create() shall return NULL]  
+	else if (messenger_config->device_id == NULL || messenger_config->iothub_host_fqdn == NULL || messenger_config->client_version == NULL)
+	{
+		LogError("Invalid argument (device_id=%p, iothub_host_fqdn=%p, client_version=%p)", 
+			messenger_config->device_id, messenger_config->iothub_host_fqdn, messenger_config->client_version);
+		twin_msgr = NULL;
+	}
+	else
+	{
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_003: [twin_messenger_create() shall allocate memory for the messenger instance structure (aka `twin_msgr`)]  
+		if ((twin_msgr = (TWIN_MESSENGER_INSTANCE*)malloc(sizeof(TWIN_MESSENGER_INSTANCE))) == NULL)
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_004: [If malloc() fails, twin_messenger_create() shall fail and return NULL]  
+			LogError("Failed allocating TWIN_MESSENGER_INSTANCE (%s)", messenger_config->device_id);
+		}
+		else
+		{
+			MAP_HANDLE link_attach_properties;
+
+			memset(twin_msgr, 0, sizeof(TWIN_MESSENGER_INSTANCE));
+			twin_msgr->state = TWIN_MESSENGER_STATE_STOPPED;
+			twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_NOT_SUBSCRIBED;
+			twin_msgr->amqp_msgr_state = AMQP_MESSENGER_STATE_STOPPED;
+
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_005: [twin_messenger_create() shall save a copy of `messenger_config` info into `twin_msgr`]  
+			if (mallocAndStrcpy_s(&twin_msgr->client_version, messenger_config->client_version) != 0)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_006: [If any `messenger_config` info fails to be copied, twin_messenger_create() shall fail and return NULL]  
+				LogError("Failed copying client_version (%s)", messenger_config->device_id);
+				internal_twin_messenger_destroy(twin_msgr);
+				twin_msgr = NULL;
+			}
+			else if (mallocAndStrcpy_s(&twin_msgr->device_id, messenger_config->device_id) != 0)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_006: [If any `messenger_config` info fails to be copied, twin_messenger_create() shall fail and return NULL]  
+				LogError("Failed copying device_id (%s)", messenger_config->device_id);
+				internal_twin_messenger_destroy(twin_msgr);
+				twin_msgr = NULL;
+			}
+			else if (mallocAndStrcpy_s(&twin_msgr->iothub_host_fqdn, messenger_config->iothub_host_fqdn) != 0)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_006: [If any `messenger_config` info fails to be copied, twin_messenger_create() shall fail and return NULL]  
+				LogError("Failed copying iothub_host_fqdn (%s)", messenger_config->device_id);
+				internal_twin_messenger_destroy(twin_msgr);
+				twin_msgr = NULL;
+			}
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_007: [`twin_msgr->pending_patches` shall be set using singlylinkedlist_create()]  
+			else if ((twin_msgr->pending_patches = singlylinkedlist_create()) == NULL)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_008: [If singlylinkedlist_create() fails, twin_messenger_create() shall fail and return NULL]   
+				LogError("Failed creating list for queueing patches (%s)", messenger_config->device_id);
+				internal_twin_messenger_destroy(twin_msgr);
+				twin_msgr = NULL;
+			}
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_009: [`twin_msgr->operations` shall be set using singlylinkedlist_create()]  
+			else if ((twin_msgr->operations = singlylinkedlist_create()) == NULL)
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_010: [If singlylinkedlist_create() fails, twin_messenger_create() shall fail and return NULL] 
+				LogError("Failed creating list for operations (%s)", messenger_config->device_id);
+				internal_twin_messenger_destroy(twin_msgr);
+				twin_msgr = NULL;
+			}
+			else if ((link_attach_properties = create_link_attach_properties(twin_msgr)) == NULL)
+			{
+				LogError("Failed creating link attach properties (%s)", messenger_config->device_id);
+				internal_twin_messenger_destroy(twin_msgr);
+				twin_msgr = NULL;
+			}
+			else
+			{
+
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_012: [`amqp_msgr_config->client_version` shall be set with `twin_msgr->client_version`]
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_013: [`amqp_msgr_config->device_id` shall be set with `twin_msgr->device_id`]
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_014: [`amqp_msgr_config->iothub_host_fqdn` shall be set with `twin_msgr->iothub_host_fqdn`]
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_015: [`amqp_msgr_config` shall have "twin/" as send link target suffix and receive link source suffix]
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_016: [`amqp_msgr_config` shall have send and receive link attach properties set as "com.microsoft:client-version" = `twin_msgr->client_version`, "com.microsoft:channel-correlation-id" = `twin:<UUID>`, "com.microsoft:api-version" = "2016-11-14"]
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_017: [`amqp_msgr_config` shall be set with `on_amqp_messenger_state_changed_callback` and `on_amqp_messenger_subscription_changed_callback` callbacks]
+				AMQP_MESSENGER_CONFIG amqp_msgr_config;
+				amqp_msgr_config.client_version = twin_msgr->client_version;
+				amqp_msgr_config.device_id = twin_msgr->device_id;
+				amqp_msgr_config.iothub_host_fqdn = twin_msgr->iothub_host_fqdn;
+				amqp_msgr_config.send_link.target_suffix = DEFAULT_TWIN_SEND_LINK_SOURCE_NAME;
+				amqp_msgr_config.send_link.attach_properties = link_attach_properties;
+				amqp_msgr_config.send_link.snd_settle_mode = sender_settle_mode_settled;
+				amqp_msgr_config.send_link.rcv_settle_mode = receiver_settle_mode_first;
+				amqp_msgr_config.receive_link.source_suffix = DEFAULT_TWIN_RECEIVE_LINK_TARGET_NAME;
+				amqp_msgr_config.receive_link.attach_properties = link_attach_properties;
+				amqp_msgr_config.receive_link.snd_settle_mode = sender_settle_mode_settled;
+				amqp_msgr_config.receive_link.rcv_settle_mode = receiver_settle_mode_first;
+				amqp_msgr_config.on_state_changed_callback = on_amqp_messenger_state_changed_callback;
+				amqp_msgr_config.on_state_changed_context = (void*)twin_msgr;
+				amqp_msgr_config.on_subscription_changed_callback = on_amqp_messenger_subscription_changed_callback;
+				amqp_msgr_config.on_subscription_changed_context = (void*)twin_msgr;
+
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_011: [`twin_msgr->amqp_msgr` shall be set using amqp_messenger_create(), passing a AMQP_MESSENGER_CONFIG instance `amqp_msgr_config`]
+				if ((twin_msgr->amqp_msgr = amqp_messenger_create(&amqp_msgr_config)) == NULL)
+				{
+					// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_018: [If amqp_messenger_create() fails, twin_messenger_create() shall fail and return NULL]  
+					LogError("Failed creating the AMQP messenger (%s)", messenger_config->device_id);
+					internal_twin_messenger_destroy(twin_msgr);
+					twin_msgr = NULL;
+				}
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_019: [`twin_msgr->amqp_msgr` shall subscribe for AMQP messages by calling amqp_messenger_subscribe_for_messages() passing `on_amqp_message_received`]  
+				else if (amqp_messenger_subscribe_for_messages(twin_msgr->amqp_msgr, on_amqp_message_received_callback, (void*)twin_msgr))
+				{
+					// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_020: [If amqp_messenger_subscribe_for_messages() fails, twin_messenger_create() shall fail and return NULL]  
+					LogError("Failed subscribing for AMQP messages (%s)", messenger_config->device_id);
+					internal_twin_messenger_destroy(twin_msgr);
+					twin_msgr = NULL;
+				}
+				else
+				{
+					// Codes_SRS_IOTHUBTRANSPORT_TWIN_MESSENGER_09_013: [`messenger_config->on_state_changed_callback` shall be saved into `twin_msgr->on_state_changed_callback`]
+					twin_msgr->on_state_changed_callback = messenger_config->on_state_changed_callback;
+
+					// Codes_SRS_IOTHUBTRANSPORT_TWIN_MESSENGER_09_014: [`messenger_config->on_state_changed_context` shall be saved into `twin_msgr->on_state_changed_context`]
+					twin_msgr->on_state_changed_context = messenger_config->on_state_changed_context;
+				}
+
+				destroy_link_attach_properties(link_attach_properties);
+			}
+		}
+	}
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_021: [If no failures occurr, twin_messenger_create() shall return a handle to `twin_msgr`]  
+	return (TWIN_MESSENGER_HANDLE)twin_msgr;
+}
+
+int twin_messenger_report_state_async(TWIN_MESSENGER_HANDLE twin_msgr_handle, CONSTBUFFER_HANDLE data, TWIN_MESSENGER_REPORT_STATE_COMPLETE_CALLBACK on_report_state_complete_callback, const void* context)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_022: [If `twin_msgr_handle` or `data` are NULL, twin_messenger_report_state_async() shall fail and return a non-zero value]  
+	if (twin_msgr_handle == NULL || data == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle=%p, data=%p)", twin_msgr_handle, data);
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+		TWIN_PATCH_OPERATION_CONTEXT* twin_patch_ctx;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_023: [twin_messenger_report_state_async() shall allocate memory for a TWIN_PATCH_OPERATION_CONTEXT structure (aka `twin_op_ctx`)]  
+		if ((twin_patch_ctx = (TWIN_PATCH_OPERATION_CONTEXT*)malloc(sizeof(TWIN_PATCH_OPERATION_CONTEXT))) == NULL)
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_024: [If malloc() fails, twin_messenger_report_state_async() shall fail and return a non-zero value]    
+			LogError("Failed creating context for sending reported state (%s)", twin_msgr->device_id);
+			result = __FAILURE__;
+		}
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_025: [`twin_op_ctx` shall have a copy of `data`]  
+		else if ((twin_patch_ctx->data = CONSTBUFFER_Clone(data)) == NULL)
+		{
+			LogError("Failed cloning TWIN patch request data (%s)", twin_msgr->device_id);
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_031: [If any failure occurs, twin_messenger_report_state_async() shall free any memory it has allocated]  
+			free(twin_patch_ctx);
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_026: [If `data` fails to be copied, twin_messenger_report_state_async() shall fail and return a non-zero value]    
+			result = __FAILURE__;
+		}
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_027: [`twin_op_ctx->time_enqueued` shall be set using get_time]    
+		else if ((twin_patch_ctx->time_enqueued = get_time(NULL)) == INDEFINITE_TIME)
+		{
+			LogError("Failed setting reported state enqueue time (%s)", twin_msgr->device_id);
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_031: [If any failure occurs, twin_messenger_report_state_async() shall free any memory it has allocated]  
+			CONSTBUFFER_Destroy(twin_patch_ctx->data);
+			free(twin_patch_ctx);
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_028: [If `twin_op_ctx->time_enqueued` fails to be set, twin_messenger_report_state_async() shall fail and return a non-zero value]    
+			result = __FAILURE__;
+		}
+		else
+		{
+			twin_patch_ctx->on_report_state_complete_callback = on_report_state_complete_callback;
+			twin_patch_ctx->on_report_state_complete_context = context;
+
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_029: [`twin_op_ctx` shall be added to `twin_msgr->pending_patches` using singlylinkedlist_add()]  
+			if (singlylinkedlist_add(twin_msgr->pending_patches, twin_patch_ctx) == NULL)
+			{
+				LogError("Failed adding TWIN patch request to queue (%s)", twin_msgr->device_id);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_031: [If any failure occurs, twin_messenger_report_state_async() shall free any memory it has allocated]  
+				CONSTBUFFER_Destroy(twin_patch_ctx->data);
+				free(twin_patch_ctx);
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_030: [If singlylinkedlist_add() fails, twin_messenger_report_state_async() shall fail and return a non-zero value]
+				result = __FAILURE__;
+			}
+			else
+			{
+				// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_032: [If no failures occur, twin_messenger_report_state_async() shall return zero]  
+				result = RESULT_OK;
+			}
+		}
+	}
+
+	return result;
+}
+
+int twin_messenger_subscribe(TWIN_MESSENGER_HANDLE twin_msgr_handle, TWIN_STATE_UPDATE_CALLBACK on_twin_state_update_callback, void* context)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_037: [If `twin_msgr_handle` or `on_twin_state_update_callback` are NULL, twin_messenger_subscribe() shall fail and return a non-zero value]  
+	if (twin_msgr_handle == NULL || on_twin_state_update_callback == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle=%p, on_twin_state_update_callback=%p)", twin_msgr_handle, on_twin_state_update_callback);
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_038: [If `twin_msgr` is already subscribed, twin_messenger_subscribe() shall return zero] 
+		if (twin_msgr->subscription_state != TWIN_SUBSCRIPTION_STATE_NOT_SUBSCRIBED)
+		{
+			result = RESULT_OK;
+		}
+		else
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_039: [`on_twin_state_update_callback` and `context` shall be saved on `twin_msgr`]
+			twin_msgr->on_message_received_callback = on_twin_state_update_callback;
+			twin_msgr->on_message_received_context = context;
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_040: [twin_messenger_subscribe() shall change `twin_msgr->subscription_state` to TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES] 
+			twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_GET_COMPLETE_PROPERTIES;
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_041: [If no failures occurr, twin_messenger_subscribe() shall return 0]  
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+int twin_messenger_unsubscribe(TWIN_MESSENGER_HANDLE twin_msgr_handle)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_042: [If `twin_msgr_handle` is NULL, twin_messenger_unsubscribe() shall fail and return a non-zero value]
+	if (twin_msgr_handle == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_043: [twin_messenger_subscribe() shall change `twin_msgr->subscription_state` to TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBE] 
+		twin_msgr->subscription_state = TWIN_SUBSCRIPTION_STATE_UNSUBSCRIBE;
+		twin_msgr->on_message_received_callback = NULL;
+		twin_msgr->on_message_received_context = NULL;
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_044: [If no failures occurr, twin_messenger_unsubscribe() shall return zero]
+		result = RESULT_OK;
+	}
+
+	return result;
+}
+
+int twin_messenger_get_send_status(TWIN_MESSENGER_HANDLE twin_msgr_handle, TWIN_MESSENGER_SEND_STATUS* send_status)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_033: [If `twin_msgr_handle` or `send_status` are NULL, twin_messenger_get_send_status() shall fail and return a non-zero value] 
+	if (twin_msgr_handle == NULL || send_status == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle=%p, send_status=%p)", twin_msgr_handle, send_status);
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+		TWIN_OPERATION_TYPE twin_op_type = TWIN_OPERATION_TYPE_PATCH;
+
+		if (singlylinkedlist_get_head_item(twin_msgr->pending_patches) != NULL || 
+			singlylinkedlist_find(twin_msgr->operations, find_twin_operation_by_type, &twin_op_type))
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_034: [If `twin_msgr->pending_patches` or `twin_msgr->operations` have any TWIN patch requests, send_status shall be set to TWIN_MESSENGER_SEND_STATUS_BUSY] 
+			*send_status = TWIN_MESSENGER_SEND_STATUS_BUSY;
+		}
+		else
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_035: [Otherwise, send_status shall be set to TWIN_MESSENGER_SEND_STATUS_IDLE] 
+			*send_status = TWIN_MESSENGER_SEND_STATUS_IDLE;
+		}
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_036: [If no failures occur, twin_messenger_get_send_status() shall return 0] 
+		result = RESULT_OK;
+	}
+
+	return result;
+}
+
+int twin_messenger_start(TWIN_MESSENGER_HANDLE twin_msgr_handle, SESSION_HANDLE session_handle)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_045: [If `twin_msgr_handle` or `session_handle` are NULL, twin_messenger_start() shall fail and return a non-zero value]
+	if (twin_msgr_handle == NULL || session_handle == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle=%p, session_handle=%p)", twin_msgr_handle, session_handle);
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_048: [If no failures occurr, `twin_msgr->state` shall be set to TWIN_MESSENGER_STATE_STARTING, and `twin_msgr->on_state_changed_callback` invoked if provided]
+		update_state(twin_msgr, TWIN_MESSENGER_STATE_STARTING);
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_046: [amqp_messenger_start() shall be invoked passing `twin_msgr->amqp_msgr` and `session_handle`]  
+		if (amqp_messenger_start(twin_msgr->amqp_msgr, session_handle) != 0)
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_047: [If amqp_messenger_start() fails, twin_messenger_start() fail and return a non-zero value]
+			LogError("Failed starting the AMQP messenger (%s)", twin_msgr->device_id);
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_049: [If any failures occurr, `twin_msgr->state` shall be set to TWIN_MESSENGER_STATE_ERROR, and `twin_msgr->on_state_changed_callback` invoked if provided]
+			update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_050: [If no failures occurr, twin_messenger_start() shall return 0]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+int twin_messenger_stop(TWIN_MESSENGER_HANDLE twin_msgr_handle)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_051: [If `twin_msgr_handle` is NULL, twin_messenger_stop() shall fail and return a non-zero value]  
+	if (twin_msgr_handle == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_054: [`twin_msgr->state` shall be set to TWIN_MESSENGER_STATE_STOPPING, and `twin_msgr->on_state_changed_callback` invoked if provided]  
+		update_state(twin_msgr, TWIN_MESSENGER_STATE_STOPPING);
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_052: [amqp_messenger_stop() shall be invoked passing `twin_msgr->amqp_msgr`]  
+		if (amqp_messenger_stop(twin_msgr->amqp_msgr) != 0)
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_053: [If amqp_messenger_stop() fails, twin_messenger_stop() fail and return a non-zero value]
+			LogError("Failed stopping the AMQP messenger (%s)", twin_msgr->device_id);
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_055: [If any failures occurr, `twin_msgr->state` shall be set to TWIN_MESSENGER_STATE_ERROR, and `twin_msgr->on_state_changed_callback` invoked if provided]
+			update_state(twin_msgr, TWIN_MESSENGER_STATE_ERROR);
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_056: [If no failures occurr, twin_messenger_stop() shall return 0]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+void twin_messenger_do_work(TWIN_MESSENGER_HANDLE twin_msgr_handle)
+{
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_057: [If `twin_msgr_handle` is NULL, twin_messenger_do_work() shall return immediately]
+	if (twin_msgr_handle != NULL)
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+
+		if (twin_msgr->state == TWIN_MESSENGER_STATE_STARTED)
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_058: [If `twin_msgr->state` is TWIN_MESSENGER_STATE_STARTED, twin_messenger_do_work() shall send the PATCHES in `twin_msgr->pending_patches`, removing them from the list]
+			(void)singlylinkedlist_remove_if(twin_msgr->pending_patches, send_pending_twin_patch, (const void*)twin_msgr);
+
+			process_twin_subscription(twin_msgr);
+		}
+
+		process_timeouts(twin_msgr);
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_083: [twin_messenger_do_work() shall invoke amqp_messenger_do_work() passing `twin_msgr->amqp_msgr`]  
+		amqp_messenger_do_work(twin_msgr->amqp_msgr);
+	}
+}
+
+void twin_messenger_destroy(TWIN_MESSENGER_HANDLE twin_msgr_handle)
+{
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_098: [If `twin_msgr_handle` is NULL, twin_messenger_destroy() shall return immediately]  
+	if (twin_msgr_handle == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle is NULL)");
+	}
+	else
+	{
+		internal_twin_messenger_destroy((TWIN_MESSENGER_INSTANCE*)twin_msgr_handle);
+	}
+}
+
+int twin_messenger_set_option(TWIN_MESSENGER_HANDLE twin_msgr_handle, const char* name, void* value)
+{
+	int result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_103: [If `twin_msgr_handle` or `name` or `value` are NULL, twin_messenger_set_option() shall fail and return a non-zero value]
+	if (twin_msgr_handle == NULL || name == NULL || value == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle=%p, name=%p, value=%p)", twin_msgr_handle, name, value);
+		result = __FAILURE__;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_104: [amqp_messenger_set_option() shall be invoked passing `name` and `option`]
+		if (amqp_messenger_set_option(twin_msgr->amqp_msgr, name, value) != RESULT_OK)
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_105: [If amqp_messenger_set_option() fails, twin_messenger_set_option() shall fail and return a non-zero value]
+			LogError("Failed setting TWIN messenger option (%s, %s)", twin_msgr->device_id, name);
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_106: [If no errors occur, twin_messenger_set_option shall return zero]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+OPTIONHANDLER_HANDLE twin_messenger_retrieve_options(TWIN_MESSENGER_HANDLE twin_msgr_handle)
+{
+	OPTIONHANDLER_HANDLE result;
+
+	// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_107: [If `twin_msgr_handle` is NULL, twin_messenger_retrieve_options shall fail and return NULL]
+	if (twin_msgr_handle == NULL)
+	{
+		LogError("Invalid argument (twin_msgr_handle is NULL)");
+		result = NULL;
+	}
+	else
+	{
+		TWIN_MESSENGER_INSTANCE* twin_msgr = (TWIN_MESSENGER_INSTANCE*)twin_msgr_handle;
+
+		// Codes_IOTHUBTRANSPORT_AMQP_TWIN_MESSENGER_09_108: [twin_messenger_retrieve_options() shall return the result of amqp_messenger_retrieve_options()]
+		if ((result = amqp_messenger_retrieve_options(twin_msgr->amqp_msgr)) == NULL)
+		{
+			LogError("Failed TWIN messenger options (%s)", twin_msgr->device_id);
+		}
+	}
+
+	return result;
+}
\ No newline at end of file