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
MQTTSingle.h
- Committer:
- icraggs
- Date:
- 2014-04-14
- Revision:
- 17:4f914fd9ee12
- Parent:
- 16:91c2f9a144d4
File content as of revision 17:4f914fd9ee12:
/******************************************************************************* * 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