An API for using MQTT over multiple transports
Dependencies: FP MQTTPacket
Dependents: Cellular_HelloMQTT IoTStarterKit GSwifiInterface_HelloMQTT IBMIoTClientEthernetExample ... more
This library is part of the EclipseTM Paho project; specifically the embedded client.
The goals of this API are:
- to be independent of any system library: hence templates parameters for networking, timer and threading classes
- not to rely on heap storage, only automatic (I think this is a good thing)
- to limit memory use, for instance by defining the size of the buffers and arrays used at object creation time
Diff: MQTTSingle.h
- Revision:
- 16:91c2f9a144d4
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/MQTTSingle.h Mon Apr 14 18:51:52 2014 +0000 @@ -0,0 +1,428 @@ +/******************************************************************************* + * Copyright (c) 2014 IBM Corp. + * + * 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 + * and the Eclipse Distribution License is available at + * http://www.eclipse.org/org/documents/edl-v10.php. + * + * Contributors: + * Ian Craggs - initial API and implementation and/or initial documentation + *******************************************************************************/ + +#if !defined(MQTTSINGLE_H) +#define MQTTSINGLE_H + +#include "FP.h" +#include "MQTTPacket.h" +#include "stdio.h" + +namespace MQTT +{ + + +enum QoS { QOS0, QOS1, QOS2 }; + + +struct Message +{ + enum QoS qos; + bool retained; + bool dup; + unsigned short id; + void *payload; + size_t payloadlen; +}; + + +class PacketId +{ +public: + PacketId(); + + int getNext(); + +private: + static const int MAX_PACKET_ID = 65535; + int next; +}; + +typedef void (*messageHandler)(Message*); + +typedef struct limits +{ + int MAX_MQTT_PACKET_SIZE; // + int MAX_MESSAGE_HANDLERS; // each subscription requires a message handler + int command_timeout; + + limits() + { + MAX_MQTT_PACKET_SIZE = 100; + MAX_MESSAGE_HANDLERS = 5; + command_timeout = 30; + } +} Limits; + + +template<class Network, class Timer> class Client +{ + +public: + + Client(Network* network, Limits* limits = 0); + + int connect(MQTTPacket_connectData* options = 0); + + int publish(const char* topic, Message* message); + + int subscribe(const char* topicFilter, enum QoS qos, messageHandler mh); + + int unsubscribe(const char* topicFilter); + + int disconnect(int timeout); + +private: + + int cycle(int timeout); + int keepalive(); + + int decodePacket(int* value, int timeout); + int readPacket(int timeout = -1); + int sendPacket(int length, int timeout = -1); + int deliverMessage(MQTTString* topic, Message* message); + + Network* ipstack; + Timer command_timer, ping_timer; + + char* buf; + int buflen; + + char* readbuf; + int readbuflen; + + unsigned int keepAliveInterval; + bool ping_outstanding; + + int command_timeout; // max time to wait for any MQTT command to complete, in seconds + PacketId packetid; + + typedef FP<void, Message*> messageHandlerFP; + struct MessageHandlers + { + char* topic; + messageHandlerFP fp; + } *messageHandlers; // Message handlers are linked to a subscription topic + int messageHandlerCount; + +}; + +} + +template<class Network, class Timer, class Thread, class Mutex> MQTT::Client<Network, Timer, Thread, Mutex>::Client(Network* network, Limits* limits) : packetid() +{ + Limits default_limits = Limits(); + + if (limits == 0) + limits = &default_limits; + + this->command_timeout = limits->command_timeout; + this->ipstack = network; + this->command_timer = Timer(); + this->ping_timer = Timer(); + this->ping_outstanding = 0; + + // How to make these memory allocations portable? I was hoping to avoid the heap + buflen = readbuflen = limits->MAX_MQTT_PACKET_SIZE; + buf = new char[limits->MAX_MQTT_PACKET_SIZE]; + readbuf = new char[limits->MAX_MQTT_PACKET_SIZE]; + this->messageHandlers = new struct MessageHandlers[limits->MAX_MESSAGE_HANDLERS]; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::sendPacket(int length, int timeout) +{ + int sent = 0; + + while (sent < length) + sent += ipstack->write(&buf[sent], length, -1); + if (sent == length) + ping_timer.reset(); // record the fact that we have successfully sent the packet + return sent; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::decodePacket(int* value, int timeout) +{ + char c; + int multiplier = 1; + int len = 0; + const int MAX_NO_OF_REMAINING_LENGTH_BYTES = 4; + + *value = 0; + do + { + int rc = MQTTPACKET_READ_ERROR; + + if (++len > MAX_NO_OF_REMAINING_LENGTH_BYTES) + { + rc = MQTTPACKET_READ_ERROR; /* bad data */ + goto exit; + } + rc = ipstack->read(&c, 1, timeout); + if (rc != 1) + goto exit; + *value += (c & 127) * multiplier; + multiplier *= 128; + } while ((c & 128) != 0); +exit: + return len; +} + + +/** + * If any read fails in this method, then we should disconnect from the network, as on reconnect + * the packets can be retried. + * @param timeout the max time to wait for the packet read to complete, in milliseconds + * @return the MQTT packet type, or -1 if none + */ +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::readPacket(int timeout) +{ + int rc = -1; + MQTTHeader header = {0}; + int len = 0; + int rem_len = 0; + + /* 1. read the header byte. This has the packet type in it */ + if (ipstack->read(readbuf, 1, timeout) != 1) + goto exit; + + len = 1; + /* 2. read the remaining length. This is variable in itself */ + decodePacket(&rem_len, timeout); + len += MQTTPacket_encode(readbuf + 1, rem_len); /* put the original remaining length back into the buffer */ + + /* 3. read the rest of the buffer using a callback to supply the rest of the data */ + if (ipstack->read(readbuf + len, rem_len, timeout) != rem_len) + goto exit; + + header.byte = readbuf[0]; + rc = header.bits.type; +exit: + return rc; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::deliverMessage(MQTTString* topic, Message* message) +{ + // we have to find the right message handler - indexed by topic +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::cycle(int timeout) +{ + /* get one piece of work off the wire and one pass through */ + + // read the socket, see what work is due + int packet_type = readPacket(timeout); + + int len, rc; + switch (packet_type) + { + case CONNACK: + case PUBACK: + case SUBACK: + break; + case PUBLISH: + MQTTString topicName; + Message msg; + rc = MQTTDeserialize_publish((int*)&msg.dup, (int*)&msg.qos, (int*)&msg.retained, (int*)&msg.id, &topicName, + (char**)&msg.payload, (int*)&msg.payloadlen, readbuf, readbuflen); + if (msg.qos == QOS0) + deliverMessage(&topicName, &msg); + break; + case PUBREC: + int type, dup, mypacketid; + if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, readbuflen) == 1) + ; + // must lock this access against the application thread, if we are multi-threaded + len = MQTTSerialize_ack(buf, buflen, PUBREL, 0, mypacketid); + rc = sendPacket(len); // send the subscribe packet + if (rc != len) + goto exit; // there was a problem + + break; + case PUBCOMP: + break; + case PINGRESP: + ping_outstanding = false; + break; + } + keepalive(); +exit: + return packet_type; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::keepalive() +{ + int rc = 0; + + if (keepAliveInterval == 0) + goto exit; + + if (ping_timer.read_ms() >= (keepAliveInterval * 1000)) + { + if (ping_outstanding) + rc = -1; + else + { + int len = MQTTSerialize_pingreq(buf, buflen); + rc = sendPacket(len); // send the connect packet + if (rc != len) + rc = -1; // indicate there's a problem + else + ping_outstanding = true; + } + } + +exit: + return rc; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::connect(MQTTPacket_connectData* options, resultHandler resultHandler) +{ + command_timer.start(); + + MQTTPacket_connectData default_options = MQTTPacket_connectData_initializer; + if (options == 0) + options = &default_options; // set default options if none were supplied + + this->keepAliveInterval = options->keepAliveInterval; + ping_timer.start(); + int len = MQTTSerialize_connect(buf, buflen, options); + int rc = sendPacket(len); // send the connect packet + if (rc != len) + goto exit; // there was a problem + + // this will be a blocking call, wait for the connack + do + { + if (command_timer.read_ms() > (command_timeout * 1000)) + goto exit; // we timed out + } + while (cycle(command_timeout - command_timer.read_ms()) != CONNACK); + int connack_rc = -1; + if (MQTTDeserialize_connack(&connack_rc, readbuf, readbuflen) == 1) + rc = connack_rc; + +exit: + command_timer.stop(); + command_timer.reset(); + return rc; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::subscribe(const char* topicFilter, enum QoS qos, messageHandler messageHandler) +{ + command_timer.start(); + + MQTTString topic = {(char*)topicFilter, 0, 0}; + + int len = MQTTSerialize_subscribe(buf, buflen, 0, packetid.getNext(), 1, &topic, (int*)&qos); + int rc = sendPacket(len); // send the subscribe packet + if (rc != len) + goto exit; // there was a problem + + // wait for suback - this will block + if (cycle(command_timeout - command_timer.read_ms()) == SUBACK) + { + int count = 0, grantedQoS = -1, mypacketid; + if (MQTTDeserialize_suback(&mypacketid, 1, &count, &grantedQoS, readbuf, readbuflen) == 1) + rc = grantedQoS; // 0, 1, 2 or 0x80 + if (rc != 0x80) + } + +exit: + command_timer.stop(); + command_timer.reset(); + return rc; +} + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::unsubscribe(const char* topicFilter, resultHandler resultHandler) +{ + command_timer.start(); + + MQTTString topic = {(char*)topicFilter, 0, 0}; + + int len = MQTTSerialize_unsubscribe(buf, buflen, 0, packetid.getNext(), 1, &topic); + int rc = sendPacket(len); // send the subscribe packet + if (rc != len) + goto exit; // there was a problem + + // this will block + if (cycle(command_timeout - command_timer.read_ms()) == UNSUBACK) + { + int mypacketid; + if (MQTTDeserialize_unsuback(&mypacketid, readbuf, readbuflen) == 1) + rc = 0; + } + +exit: + command_timer.stop(); + command_timer.reset(); + return rc; +} + + + +template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::publish(const char* topicName, Message* message, resultHandler resultHandler) +{ + command_timer.start(); + + MQTTString topic = {(char*)topicName, 0, 0}; + + message->id = packetid.getNext(); + + int len = MQTTSerialize_publish(buf, buflen, 0, message->qos, message->retained, message->id, topic, message->payload, message->payloadlen); + int rc = sendPacket(len); // send the subscribe packet + if (rc != len) + goto exit; // there was a problem + + /* wait for acks */ + if (resultHandler == 0) + { + if (message->qos == QOS1) + { + if (cycle(command_timeout - command_timer.read_ms()) == PUBACK) + { + int type, dup, mypacketid; + if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, readbuflen) == 1) + rc = 0; + } + } + else if (message->qos == QOS2) + { + if (cycle(command_timeout - command_timer.read_ms()) == PUBCOMP) + { + int type, dup, mypacketid; + if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, readbuflen) == 1) + rc = 0; + } + + } + } + +exit: + command_timer.stop(); + command_timer.reset(); + return rc; +} + + +#endif