Diff: core/liblwm2m.h

Revision:

0:3f48af28ebcd

diff -r 000000000000 -r 3f48af28ebcd core/liblwm2m.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/liblwm2m.h	Wed Apr 19 11:28:00 2017 +0000
@@ -0,0 +1,740 @@
+/*******************************************************************************
+ *
+ * Copyright (c) 2013, 2014 Intel Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * and Eclipse Distribution License v1.0 which accompany this distribution.
+ *
+ * The Eclipse Public License is available at
+ *    http://www.eclipse.org/legal/epl-v10.html
+ * The Eclipse Distribution License is available at
+ *    http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * Contributors:
+ *    David Navarro, Intel Corporation - initial API and implementation
+ *    Fabien Fleutot - Please refer to git log
+ *    Simon Bernard - Please refer to git log
+ *    Toby Jaffey - Please refer to git log
+ *    Julien Vermillard - Please refer to git log
+ *    Bosch Software Innovations GmbH - Please refer to git log
+ *    Pascal Rieux - Please refer to git log
+ *******************************************************************************/
+
+/*
+ Copyright (c) 2013, 2014 Intel Corporation
+
+ Redistribution and use in source and binary forms, with or without modification,
+ are permitted provided that the following conditions are met:
+
+     * Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+     * Redistributions in binary form must reproduce the above copyright notice,
+       this list of conditions and the following disclaimer in the documentation
+       and/or other materials provided with the distribution.
+     * Neither the name of Intel Corporation nor the names of its contributors
+       may be used to endorse or promote products derived from this software
+       without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ THE POSSIBILITY OF SUCH DAMAGE.
+
+ David Navarro <david.navarro@intel.com>
+
+*/
+
+#ifndef _LWM2M_CLIENT_H_
+#define _LWM2M_CLIENT_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <time.h>
+
+#ifdef LWM2M_SERVER_MODE
+#ifndef LWM2M_SUPPORT_JSON
+#define LWM2M_SUPPORT_JSON
+#endif
+#endif
+
+#if defined(LWM2M_BOOTSTRAP) && defined(LWM2M_BOOTSTRAP_SERVER_MODE)
+#error "LWM2M_BOOTSTRAP and LWM2M_BOOTSTRAP_SERVER_MODE cannot be defined at the same time!"
+#endif
+
+/*
+ * Platform abstraction functions to be implemented by the user
+ */
+
+#ifndef LWM2M_MEMORY_TRACE
+// Allocate a block of size bytes of memory, returning a pointer to the beginning of the block.
+void * lwm2m_malloc(size_t s);
+// Deallocate a block of memory previously allocated by lwm2m_malloc() or lwm2m_strdup()
+void lwm2m_free(void * p);
+// Allocate a memory block, duplicate the string str in it and return a pointer to this new block.
+char * lwm2m_strdup(const char * str);
+#else
+// same functions as above with caller location for debugging purposes
+char * lwm2m_trace_strdup(const char * str, const char * file, const char * function, int lineno);
+void * lwm2m_trace_malloc(size_t size, const char * file, const char * function, int lineno);
+void    lwm2m_trace_free(void * mem, const char * file, const char * function, int lineno);
+
+#define lwm2m_strdup(S) lwm2m_trace_strdup(S, __FILE__, __FUNCTION__, __LINE__)
+#define lwm2m_malloc(S) lwm2m_trace_malloc(S, __FILE__, __FUNCTION__, __LINE__)
+#define lwm2m_free(M)   lwm2m_trace_free(M, __FILE__, __FUNCTION__, __LINE__)
+#endif
+// Compare at most the n first bytes of s1 and s2, return 0 if they match
+int lwm2m_strncmp(const char * s1, const char * s2, size_t n);
+// This function must return the number of seconds elapsed since origin.
+// The origin (Epoch, system boot, etc...) does not matter as this
+// function is used only to determine the elapsed time since the last
+// call to it.
+// In case of error, this must return a negative value.
+// Per POSIX specifications, time_t is a signed integer.
+time_t lwm2m_gettime(void);
+
+#ifdef LWM2M_WITH_LOGS
+// Same usage as C89 printf()
+void lwm2m_printf(const char * format, ...);
+#endif
+
+// communication layer
+#ifdef LWM2M_CLIENT_MODE
+// Returns a session handle that MUST uniquely identify a peer.
+// secObjInstID: ID of the Securty Object instance to open a connection to
+// userData: parameter to lwm2m_init()
+void * lwm2m_connect_server(uint16_t secObjInstID, void * userData);
+// Close a session created by lwm2m_connect_server()
+// sessionH: session handle identifying the peer (opaque to the core)
+// userData: parameter to lwm2m_init()
+void lwm2m_close_connection(void * sessionH, void * userData);
+#endif
+// Send data to a peer
+// Returns COAP_NO_ERROR or a COAP_NNN error code
+// sessionH: session handle identifying the peer (opaque to the core)
+// buffer, length: data to send
+// userData: parameter to lwm2m_init()
+uint8_t lwm2m_buffer_send(void * sessionH, uint8_t * buffer, size_t length, void * userData);
+// Compare two session handles
+// Returns true if the two sessions identify the same peer. false otherwise.
+// userData: parameter to lwm2m_init()
+bool lwm2m_session_is_equal(void * session1, void * session2, void * userData);
+
+/*
+ * Error code
+ */
+
+#define COAP_NO_ERROR                   (uint8_t)0x00
+#define COAP_IGNORE                     (uint8_t)0x01
+
+#define COAP_201_CREATED                (uint8_t)0x41
+#define COAP_202_DELETED                (uint8_t)0x42
+#define COAP_204_CHANGED                (uint8_t)0x44
+#define COAP_205_CONTENT                (uint8_t)0x45
+#define COAP_231_CONTINUE               (uint8_t)0x5F
+#define COAP_400_BAD_REQUEST            (uint8_t)0x80
+#define COAP_401_UNAUTHORIZED           (uint8_t)0x81
+#define COAP_402_BAD_OPTION             (uint8_t)0x82
+#define COAP_404_NOT_FOUND              (uint8_t)0x84
+#define COAP_405_METHOD_NOT_ALLOWED     (uint8_t)0x85
+#define COAP_406_NOT_ACCEPTABLE         (uint8_t)0x86
+#define COAP_408_REQ_ENTITY_INCOMPLETE  (uint8_t)0x88
+#define COAP_412_PRECONDITION_FAILED    (uint8_t)0x8C
+#define COAP_413_ENTITY_TOO_LARGE       (uint8_t)0x8D
+#define COAP_500_INTERNAL_SERVER_ERROR  (uint8_t)0xA0
+#define COAP_501_NOT_IMPLEMENTED        (uint8_t)0xA1
+#define COAP_503_SERVICE_UNAVAILABLE    (uint8_t)0xA3
+
+/*
+ * Standard Object IDs
+ */
+#define LWM2M_SECURITY_OBJECT_ID            0
+#define LWM2M_SERVER_OBJECT_ID              1
+#define LWM2M_ACL_OBJECT_ID                 2
+#define LWM2M_DEVICE_OBJECT_ID              3
+#define LWM2M_CONN_MONITOR_OBJECT_ID        4
+#define LWM2M_FIRMWARE_UPDATE_OBJECT_ID     5
+#define LWM2M_LOCATION_OBJECT_ID            6
+#define LWM2M_CONN_STATS_OBJECT_ID          7
+
+/*
+ * Ressource IDs for the LWM2M Security Object
+ */
+#define LWM2M_SECURITY_URI_ID                 0
+#define LWM2M_SECURITY_BOOTSTRAP_ID           1
+#define LWM2M_SECURITY_SECURITY_ID            2
+#define LWM2M_SECURITY_PUBLIC_KEY_ID          3
+#define LWM2M_SECURITY_SERVER_PUBLIC_KEY_ID   4
+#define LWM2M_SECURITY_SECRET_KEY_ID          5
+#define LWM2M_SECURITY_SMS_SECURITY_ID        6
+#define LWM2M_SECURITY_SMS_KEY_PARAM_ID       7
+#define LWM2M_SECURITY_SMS_SECRET_KEY_ID      8
+#define LWM2M_SECURITY_SMS_SERVER_NUMBER_ID   9
+#define LWM2M_SECURITY_SHORT_SERVER_ID        10
+#define LWM2M_SECURITY_HOLD_OFF_ID            11
+#define LWM2M_SECURITY_BOOTSTRAP_TIMEOUT_ID   12
+
+/*
+ * Ressource IDs for the LWM2M Server Object
+ */
+#define LWM2M_SERVER_SHORT_ID_ID    0
+#define LWM2M_SERVER_LIFETIME_ID    1
+#define LWM2M_SERVER_MIN_PERIOD_ID  2
+#define LWM2M_SERVER_MAX_PERIOD_ID  3
+#define LWM2M_SERVER_DISABLE_ID     4
+#define LWM2M_SERVER_TIMEOUT_ID     5
+#define LWM2M_SERVER_STORING_ID     6
+#define LWM2M_SERVER_BINDING_ID     7
+#define LWM2M_SERVER_UPDATE_ID      8
+
+#define LWM2M_SECURITY_MODE_PRE_SHARED_KEY  0
+#define LWM2M_SECURITY_MODE_RAW_PUBLIC_KEY  1
+#define LWM2M_SECURITY_MODE_CERTIFICATE     2
+#define LWM2M_SECURITY_MODE_NONE            3
+
+
+/*
+ * Utility functions for sorted linked list
+ */
+
+typedef struct _lwm2m_list_t
+{
+    struct _lwm2m_list_t * next;
+    uint16_t    id;
+} lwm2m_list_t;
+
+// defined in list.c
+// Add 'node' to the list 'head' and return the new list
+lwm2m_list_t * lwm2m_list_add(lwm2m_list_t * head, lwm2m_list_t * node);
+// Return the node with ID 'id' from the list 'head' or NULL if not found
+lwm2m_list_t * lwm2m_list_find(lwm2m_list_t * head, uint16_t id);
+// Remove the node with ID 'id' from the list 'head' and return the new list
+lwm2m_list_t * lwm2m_list_remove(lwm2m_list_t * head, uint16_t id, lwm2m_list_t ** nodeP);
+// Return the lowest unused ID in the list 'head'
+uint16_t lwm2m_list_newId(lwm2m_list_t * head);
+// Free a list. Do not use if nodes contain allocated pointers as it calls lwm2m_free on nodes only.
+// If the nodes of the list need to do more than just "free()" their instances, don't use lwm2m_list_free().
+void lwm2m_list_free(lwm2m_list_t * head);
+
+#define LWM2M_LIST_ADD(H,N) lwm2m_list_add((lwm2m_list_t *)H, (lwm2m_list_t *)N);
+#define LWM2M_LIST_RM(H,I,N) lwm2m_list_remove((lwm2m_list_t *)H, I, (lwm2m_list_t **)N);
+#define LWM2M_LIST_FIND(H,I) lwm2m_list_find((lwm2m_list_t *)H, I)
+#define LWM2M_LIST_FREE(H) lwm2m_list_free((lwm2m_list_t *)H)
+
+/*
+ * URI
+ *
+ * objectId is always set
+ * instanceId or resourceId are set according to the flag bit-field
+ *
+ */
+
+#define LWM2M_MAX_ID   ((uint16_t)0xFFFF)
+
+#define LWM2M_URI_FLAG_OBJECT_ID    (uint8_t)0x04
+#define LWM2M_URI_FLAG_INSTANCE_ID  (uint8_t)0x02
+#define LWM2M_URI_FLAG_RESOURCE_ID  (uint8_t)0x01
+
+#define LWM2M_URI_IS_SET_INSTANCE(uri) (((uri)->flag & LWM2M_URI_FLAG_INSTANCE_ID) != 0)
+#define LWM2M_URI_IS_SET_RESOURCE(uri) (((uri)->flag & LWM2M_URI_FLAG_RESOURCE_ID) != 0)
+
+typedef struct
+{
+    uint8_t     flag;           // indicates which segments are set
+    uint16_t    objectId;
+    uint16_t    instanceId;
+    uint16_t    resourceId;
+} lwm2m_uri_t;
+
+
+#define LWM2M_STRING_ID_MAX_LEN 6
+
+// Parse an URI in LWM2M format and fill the lwm2m_uri_t.
+// Return the number of characters read from buffer or 0 in case of error.
+// Valid URIs: /1, /1/, /1/2, /1/2/, /1/2/3
+// Invalid URIs: /, //, //2, /1//, /1//3, /1/2/3/, /1/2/3/4
+int lwm2m_stringToUri(const char * buffer, size_t buffer_len, lwm2m_uri_t * uriP);
+
+/*
+ * The lwm2m_data_t is used to store LWM2M resource values in a hierarchical way.
+ * Depending on the type the value is different:
+ * - LWM2M_TYPE_OBJECT, LWM2M_TYPE_OBJECT_INSTANCE, LWM2M_TYPE_MULTIPLE_RESOURCE: value.asChildren
+ * - LWM2M_TYPE_STRING, LWM2M_TYPE_OPAQUE: value.asBuffer
+ * - LWM2M_TYPE_INTEGER, LWM2M_TYPE_TIME: value.asInteger
+ * - LWM2M_TYPE_FLOAT: value.asFloat
+ * - LWM2M_TYPE_BOOLEAN: value.asBoolean
+ *
+ * LWM2M_TYPE_STRING is also used when the data is in text format.
+ */
+
+typedef enum
+{
+    LWM2M_TYPE_UNDEFINED = 0,
+    LWM2M_TYPE_OBJECT,
+    LWM2M_TYPE_OBJECT_INSTANCE,
+    LWM2M_TYPE_MULTIPLE_RESOURCE,
+
+    LWM2M_TYPE_STRING,
+    LWM2M_TYPE_OPAQUE,
+    LWM2M_TYPE_INTEGER,
+    LWM2M_TYPE_FLOAT,
+    LWM2M_TYPE_BOOLEAN,
+
+    LWM2M_TYPE_OBJECT_LINK
+} lwm2m_data_type_t;
+
+typedef struct _lwm2m_data_t lwm2m_data_t;
+
+struct _lwm2m_data_t
+{
+    lwm2m_data_type_t type;
+    uint16_t    id;
+    union
+    {
+        bool        asBoolean;
+        int64_t     asInteger;
+        double      asFloat;
+        struct
+        {
+            size_t    length;
+            uint8_t * buffer;
+        } asBuffer;
+        struct
+        {
+            size_t         count;
+            lwm2m_data_t * array;
+        } asChildren;
+        struct
+        {
+            uint16_t objectId;
+            uint16_t objectInstanceId;
+        } asObjLink;
+    } value;
+};
+
+typedef enum
+{
+    LWM2M_CONTENT_TEXT      = 0,        // Also used as undefined
+    LWM2M_CONTENT_LINK      = 40,
+    LWM2M_CONTENT_OPAQUE    = 42,
+    LWM2M_CONTENT_TLV_OLD   = 1542,     // Keep old value for backward-compatibility
+    LWM2M_CONTENT_TLV       = 11542,
+    LWM2M_CONTENT_JSON_OLD  = 1543,     // Keep old value for backward-compatibility
+    LWM2M_CONTENT_JSON      = 11543
+} lwm2m_media_type_t;
+
+lwm2m_data_t * lwm2m_data_new(int size);
+int lwm2m_data_parse(lwm2m_uri_t * uriP, uint8_t * buffer, size_t bufferLen, lwm2m_media_type_t format, lwm2m_data_t ** dataP);
+int lwm2m_data_serialize(lwm2m_uri_t * uriP, int size, lwm2m_data_t * dataP, lwm2m_media_type_t * formatP, uint8_t ** bufferP);
+void lwm2m_data_free(int size, lwm2m_data_t * dataP);
+
+void lwm2m_data_encode_string(const char * string, lwm2m_data_t * dataP);
+void lwm2m_data_encode_nstring(const char * string, size_t length, lwm2m_data_t * dataP);
+void lwm2m_data_encode_opaque(uint8_t * buffer, size_t length, lwm2m_data_t * dataP);
+void lwm2m_data_encode_int(int64_t value, lwm2m_data_t * dataP);
+int lwm2m_data_decode_int(const lwm2m_data_t * dataP, int64_t * valueP);
+void lwm2m_data_encode_float(double value, lwm2m_data_t * dataP);
+int lwm2m_data_decode_float(const lwm2m_data_t * dataP, double * valueP);
+void lwm2m_data_encode_bool(bool value, lwm2m_data_t * dataP);
+int lwm2m_data_decode_bool(const lwm2m_data_t * dataP, bool * valueP);
+void lwm2m_data_encode_objlink(uint16_t objectId, uint16_t objectInstanceId, lwm2m_data_t * dataP);
+void lwm2m_data_encode_instances(lwm2m_data_t * subDataP, size_t count, lwm2m_data_t * dataP);
+void lwm2m_data_include(lwm2m_data_t * subDataP, size_t count, lwm2m_data_t * dataP);
+
+
+/*
+ * Utility function to parse TLV buffers directly
+ *
+ * Returned value: number of bytes parsed
+ * buffer: buffer to parse
+ * buffer_len: length in bytes of buffer
+ * oType: (OUT) type of the parsed TLV record. can be:
+ *          - LWM2M_TYPE_OBJECT
+ *          - LWM2M_TYPE_OBJECT_INSTANCE
+ *          - LWM2M_TYPE_MULTIPLE_RESOURCE
+ *          - LWM2M_TYPE_OPAQUE
+ * oID: (OUT) ID of the parsed TLV record
+ * oDataIndex: (OUT) index of the data of the parsed TLV record in the buffer
+ * oDataLen: (OUT) length of the data of the parsed TLV record
+ */
+
+#define LWM2M_TLV_HEADER_MAX_LENGTH 6
+
+int lwm2m_decode_TLV(const uint8_t * buffer, size_t buffer_len, lwm2m_data_type_t * oType, uint16_t * oID, size_t * oDataIndex, size_t * oDataLen);
+
+
+/*
+ * LWM2M Objects
+ *
+ * For the read callback, if *numDataP is not zero, *dataArrayP is pre-allocated
+ * and contains the list of resources to read.
+ *
+ */
+
+typedef struct _lwm2m_object_t lwm2m_object_t;
+
+typedef uint8_t (*lwm2m_read_callback_t) (uint16_t instanceId, int * numDataP, lwm2m_data_t ** dataArrayP, lwm2m_object_t * objectP);
+typedef uint8_t (*lwm2m_discover_callback_t) (uint16_t instanceId, int * numDataP, lwm2m_data_t ** dataArrayP, lwm2m_object_t * objectP);
+typedef uint8_t (*lwm2m_write_callback_t) (uint16_t instanceId, int numData, lwm2m_data_t * dataArray, lwm2m_object_t * objectP);
+typedef uint8_t (*lwm2m_execute_callback_t) (uint16_t instanceId, uint16_t resourceId, uint8_t * buffer, int length, lwm2m_object_t * objectP);
+typedef uint8_t (*lwm2m_create_callback_t) (uint16_t instanceId, int numData, lwm2m_data_t * dataArray, lwm2m_object_t * objectP);
+typedef uint8_t (*lwm2m_delete_callback_t) (uint16_t instanceId, lwm2m_object_t * objectP);
+
+struct _lwm2m_object_t
+{
+    struct _lwm2m_object_t * next;           // for internal use only.
+    uint16_t       objID;
+    lwm2m_list_t * instanceList;
+    lwm2m_read_callback_t     readFunc;
+    lwm2m_write_callback_t    writeFunc;
+    lwm2m_execute_callback_t  executeFunc;
+    lwm2m_create_callback_t   createFunc;
+    lwm2m_delete_callback_t   deleteFunc;
+    lwm2m_discover_callback_t discoverFunc;
+    void * userData;
+};
+
+/*
+ * LWM2M Servers
+ *
+ * Since LWM2M Server Object instances are not accessible to LWM2M servers,
+ * there is no need to store them as lwm2m_objects_t
+ */
+
+typedef enum
+{
+    STATE_DEREGISTERED = 0,        // not registered or boostrap not started
+    STATE_REG_PENDING,             // registration pending
+    STATE_REGISTERED,              // successfully registered
+    STATE_REG_FAILED,              // last registration failed
+    STATE_REG_UPDATE_PENDING,      // registration update pending
+    STATE_REG_UPDATE_NEEDED,       // registration update required
+    STATE_REG_FULL_UPDATE_NEEDED,  // registration update with objects required
+    STATE_DEREG_PENDING,           // deregistration pending
+    STATE_BS_HOLD_OFF,             // bootstrap hold off time
+    STATE_BS_INITIATED,            // bootstrap request sent
+    STATE_BS_PENDING,              // boostrap ongoing
+    STATE_BS_FINISHING,            // boostrap finish received
+    STATE_BS_FINISHED,             // bootstrap done
+    STATE_BS_FAILING,              // bootstrap error occurred
+    STATE_BS_FAILED,               // bootstrap failed
+} lwm2m_status_t;
+
+typedef enum
+{
+    BINDING_UNKNOWN = 0,
+    BINDING_U,   // UDP
+    BINDING_UQ,  // UDP queue mode
+    BINDING_S,   // SMS
+    BINDING_SQ,  // SMS queue mode
+    BINDING_US,  // UDP plus SMS
+    BINDING_UQS  // UDP queue mode plus SMS
+} lwm2m_binding_t;
+
+/*
+ * LWM2M block1 data
+ *
+ * Temporary data needed to handle block1 request.
+ * Currently support only one block1 request by server.
+ */
+typedef struct _lwm2m_block1_data_ lwm2m_block1_data_t;
+
+struct _lwm2m_block1_data_
+{
+    uint8_t *             block1buffer;     // data buffer
+    size_t                block1bufferSize; // buffer size
+    uint16_t              lastmid;          // mid of the last message received
+};
+
+typedef struct _lwm2m_server_
+{
+    struct _lwm2m_server_ * next;         // matches lwm2m_list_t::next
+    uint16_t                secObjInstID; // matches lwm2m_list_t::id
+    uint16_t                shortID;      // servers short ID, may be 0 for bootstrap server
+    time_t                  lifetime;     // lifetime of the registration in sec or 0 if default value (86400 sec), also used as hold off time for bootstrap servers
+    time_t                  registration; // date of the last registration in sec or end of client hold off time for bootstrap servers
+    lwm2m_binding_t         binding;      // client connection mode with this server
+    void *                  sessionH;
+    lwm2m_status_t          status;
+    char *                  location;
+    bool                    dirty;
+    lwm2m_block1_data_t *   block1Data;   // buffer to handle block1 data, should be replace by a list to support several block1 transfer by server.
+} lwm2m_server_t;
+
+
+/*
+ * LWM2M result callback
+ *
+ * When used with an observe, if 'data' is not nil, 'status' holds the observe counter.
+ */
+typedef void (*lwm2m_result_callback_t) (uint16_t clientID, lwm2m_uri_t * uriP, int status, lwm2m_media_type_t format, uint8_t * data, int dataLength, void * userData);
+
+/*
+ * LWM2M Observations
+ *
+ * Used to store observation of remote clients resources.
+ * status STATE_REG_PENDING means the observe request was sent to the client but not yet answered.
+ * status STATE_REGISTERED means the client acknowledged the observe request.
+ * status STATE_DEREG_PENDING means the user canceled the request before the client answered it.
+ */
+
+typedef struct _lwm2m_observation_
+{
+    struct _lwm2m_observation_ * next;  // matches lwm2m_list_t::next
+    uint16_t                     id;    // matches lwm2m_list_t::id
+    struct _lwm2m_client_ * clientP;
+    lwm2m_uri_t             uri;
+    lwm2m_status_t          status;
+    lwm2m_result_callback_t callback;
+    void *                  userData;
+} lwm2m_observation_t;
+
+/*
+ * LWM2M Link Attributes
+ *
+ * Used for observation parameters.
+ *
+ */
+
+#define LWM2M_ATTR_FLAG_MIN_PERIOD      (uint8_t)0x01
+#define LWM2M_ATTR_FLAG_MAX_PERIOD      (uint8_t)0x02
+#define LWM2M_ATTR_FLAG_GREATER_THAN    (uint8_t)0x04
+#define LWM2M_ATTR_FLAG_LESS_THAN       (uint8_t)0x08
+#define LWM2M_ATTR_FLAG_STEP            (uint8_t)0x10
+
+typedef struct
+{
+    uint8_t     toSet;
+    uint8_t     toClear;
+    uint32_t    minPeriod;
+    uint32_t    maxPeriod;
+    double      greaterThan;
+    double      lessThan;
+    double      step;
+} lwm2m_attributes_t;
+
+/*
+ * LWM2M Clients
+ *
+ * Be careful not to mix lwm2m_client_object_t used to store list of objects of remote clients
+ * and lwm2m_object_t describing objects exposed to remote servers.
+ *
+ */
+
+typedef struct _lwm2m_client_object_
+{
+    struct _lwm2m_client_object_ * next; // matches lwm2m_list_t::next
+    uint16_t                 id;         // matches lwm2m_list_t::id
+    lwm2m_list_t *           instanceList;
+} lwm2m_client_object_t;
+
+typedef struct _lwm2m_client_
+{
+    struct _lwm2m_client_ * next;       // matches lwm2m_list_t::next
+    uint16_t                internalID; // matches lwm2m_list_t::id
+    char *                  name;
+    lwm2m_binding_t         binding;
+    char *                  msisdn;
+    char *                  altPath;
+    bool                    supportJSON;
+    uint32_t                lifetime;
+    time_t                  endOfLife;
+    void *                  sessionH;
+    lwm2m_client_object_t * objectList;
+    lwm2m_observation_t *   observationList;
+} lwm2m_client_t;
+
+
+/*
+ * LWM2M transaction
+ *
+ * Adaptation of Erbium's coap_transaction_t
+ */
+
+typedef struct _lwm2m_transaction_ lwm2m_transaction_t;
+
+typedef void (*lwm2m_transaction_callback_t) (lwm2m_transaction_t * transacP, void * message);
+
+struct _lwm2m_transaction_
+{
+    lwm2m_transaction_t * next;  // matches lwm2m_list_t::next
+    uint16_t              mID;   // matches lwm2m_list_t::id
+    void *                peerH;
+    uint8_t               ack_received; // indicates, that the ACK was received
+    time_t                response_timeout; // timeout to wait for response, if token is used. When 0, use calculated acknowledge timeout.
+    uint8_t  retrans_counter;
+    time_t   retrans_time;
+    char objStringID[LWM2M_STRING_ID_MAX_LEN];
+    char instanceStringID[LWM2M_STRING_ID_MAX_LEN];
+    char resourceStringID[LWM2M_STRING_ID_MAX_LEN];
+    void * message;
+    uint16_t buffer_len;
+    uint8_t * buffer;
+    lwm2m_transaction_callback_t callback;
+    void * userData;
+};
+
+/*
+ * LWM2M observed resources
+ */
+typedef struct _lwm2m_watcher_
+{
+    struct _lwm2m_watcher_ * next;
+
+    bool active;
+    bool update;
+    lwm2m_server_t * server;
+    lwm2m_attributes_t * parameters;
+    uint8_t token[8];
+    size_t tokenLen;
+    time_t lastTime;
+    uint32_t counter;
+    uint16_t lastMid;
+    union
+    {
+        int64_t asInteger;
+        double  asFloat;
+    } lastValue;
+} lwm2m_watcher_t;
+
+typedef struct _lwm2m_observed_
+{
+    struct _lwm2m_observed_ * next;
+
+    lwm2m_uri_t uri;
+    lwm2m_watcher_t * watcherList;
+} lwm2m_observed_t;
+
+#ifdef LWM2M_CLIENT_MODE
+
+typedef enum
+{
+    STATE_INITIAL = 0,
+    STATE_BOOTSTRAP_REQUIRED,
+    STATE_BOOTSTRAPPING,
+    STATE_REGISTER_REQUIRED,
+    STATE_REGISTERING,
+    STATE_READY
+} lwm2m_client_state_t;
+
+#endif
+/*
+ * LWM2M Context
+ */
+
+#ifdef LWM2M_BOOTSTRAP_SERVER_MODE
+// In all the following APIs, the session handle MUST uniquely identify a peer.
+
+// LWM2M bootstrap callback
+// When a LWM2M client requests bootstrap information, the callback is called with status COAP_NO_ERROR, uriP is nil and
+// name is set. The callback must return a COAP_* error code. COAP_204_CHANGED for success.
+// After a lwm2m_bootstrap_delete() or a lwm2m_bootstrap_write(), the callback is called with the status returned by the
+// client, the URI of the operation (may be nil) and name is nil. The callback return value is ignored.
+typedef int (*lwm2m_bootstrap_callback_t) (void * sessionH, uint8_t status, lwm2m_uri_t * uriP, char * name, void * userData);
+#endif
+
+typedef struct
+{
+#ifdef LWM2M_CLIENT_MODE
+    lwm2m_client_state_t state;
+    char *               endpointName;
+    char *               msisdn;
+    char *               altPath;
+    lwm2m_server_t *     bootstrapServerList;
+    lwm2m_server_t *     serverList;
+    lwm2m_object_t *     objectList;
+    lwm2m_observed_t *   observedList;
+#endif
+#ifdef LWM2M_SERVER_MODE
+    lwm2m_client_t *        clientList;
+    lwm2m_result_callback_t monitorCallback;
+    void *                  monitorUserData;
+#endif
+#ifdef LWM2M_BOOTSTRAP_SERVER_MODE
+    lwm2m_bootstrap_callback_t bootstrapCallback;
+    void *                     bootstrapUserData;
+#endif
+    uint16_t                nextMID;
+    lwm2m_transaction_t *   transactionList;
+    void *                  userData;
+} lwm2m_context_t;
+
+
+// initialize a liblwm2m context.
+lwm2m_context_t * lwm2m_init(void * userData);
+// close a liblwm2m context.
+void lwm2m_close(lwm2m_context_t * contextP);
+
+// perform any required pending operation and adjust timeoutP to the maximal time interval to wait in seconds.
+int lwm2m_step(lwm2m_context_t * contextP, time_t * timeoutP);
+// dispatch received data to liblwm2m
+void lwm2m_handle_packet(lwm2m_context_t * contextP, uint8_t * buffer, int length, void * fromSessionH);
+
+#ifdef LWM2M_CLIENT_MODE
+// configure the client side with the Endpoint Name, binding, MSISDN (can be nil), alternative path
+// for objects (can be nil) and a list of objects.
+// LWM2M Security Object (ID 0) must be present with either a bootstrap server or a LWM2M server and
+// its matching LWM2M Server Object (ID 1) instance
+int lwm2m_configure(lwm2m_context_t * contextP, const char * endpointName, const char * msisdn, const char * altPath, uint16_t numObject, lwm2m_object_t * objectList[]);
+int lwm2m_add_object(lwm2m_context_t * contextP, lwm2m_object_t * objectP);
+int lwm2m_remove_object(lwm2m_context_t * contextP, uint16_t id);
+
+// send a registration update to the server specified by the server short identifier
+// or all if the ID is 0.
+// If withObjects is true, the registration update contains the object list.
+int lwm2m_update_registration(lwm2m_context_t * contextP, uint16_t shortServerID, bool withObjects);
+
+void lwm2m_resource_value_changed(lwm2m_context_t * contextP, lwm2m_uri_t * uriP);
+#endif
+
+#ifdef LWM2M_SERVER_MODE
+// Clients registration/deregistration monitoring API.
+// When a LWM2M client registers, the callback is called with status COAP_201_CREATED.
+// When a LWM2M client deregisters, the callback is called with status COAP_202_DELETED.
+// clientID is the internal ID of the LWM2M Client.
+// The callback's parameters uri, data, dataLength are always NULL.
+// The lwm2m_client_t is present in the lwm2m_context_t's clientList when the callback is called. On a deregistration, it deleted when the callback returns.
+void lwm2m_set_monitoring_callback(lwm2m_context_t * contextP, lwm2m_result_callback_t callback, void * userData);
+
+// Device Management APIs
+int lwm2m_dm_read(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_dm_discover(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_dm_write(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_media_type_t format, uint8_t * buffer, int length, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_dm_write_attributes(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_attributes_t * attrP, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_dm_execute(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_media_type_t format, uint8_t * buffer, int length, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_dm_create(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_media_type_t format, uint8_t * buffer, int length, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_dm_delete(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_result_callback_t callback, void * userData);
+
+// Information Reporting APIs
+int lwm2m_observe(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_result_callback_t callback, void * userData);
+int lwm2m_observe_cancel(lwm2m_context_t * contextP, uint16_t clientID, lwm2m_uri_t * uriP, lwm2m_result_callback_t callback, void * userData);
+#endif
+
+#ifdef LWM2M_BOOTSTRAP_SERVER_MODE
+// Clients bootstrap request monitoring API.
+// When a LWM2M client sends a bootstrap request, the callback is called with the client's endpoint name.
+void lwm2m_set_bootstrap_callback(lwm2m_context_t * contextP, lwm2m_bootstrap_callback_t callback, void * userData);
+
+// Boostrap Interface APIs
+// if uriP is nil, a "Delete /" is sent to the client
+int lwm2m_bootstrap_delete(lwm2m_context_t * contextP, void * sessionH, lwm2m_uri_t * uriP);
+int lwm2m_bootstrap_write(lwm2m_context_t * contextP, void * sessionH, lwm2m_uri_t * uriP, lwm2m_media_type_t format, uint8_t * buffer, size_t length);
+int lwm2m_bootstrap_finish(lwm2m_context_t * contextP, void * sessionH);
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif