![](/media/cache/group/mqtt.png.50x50_q85.png)
Sample MQTT program - simple send and receive
This program and the MQTT libraries it uses are part of the EclipseTM Paho project; specifically the embedded client.
This example and API are working, but are still in progress. Please give us your feedback.
HelloMQTT is an example of using the MQTT API. The MQTT API is portable across network interface stacks. MQTT is designed to be used with TCP/IP, but any transport with similar characteristics should be suitable.
HelloMQTT uses the NetworkInterface APIs in mbed OS 5 to show how this works. The MQTT library contains an MQTTNetwork.h header, which is a wrapper around the mbed networking interface. To switch between connectivity methods (the default is Ethernet) the easy-connect library is provided in this example application. You can change the connectivity method in mbed_app.json
.
Adding new connectivity methods to the program is trivial, as long as they implement the mbed OS 5 NetworkStack
API.
Diff: main_linux.cpp
- Revision:
- 3:7a6a899de7cc
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/main_linux.cpp Tue May 06 09:45:22 2014 +0000 @@ -0,0 +1,324 @@ +/******************************************************************************* + * 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 + *******************************************************************************/ + + /** + This is a sample program to illustrate the use of the MQTT Client library + on Linux. The Client class requires two classes which mediate + access to system interfaces for networking and timing. As long as these two + classes provide the required public programming interfaces, it does not matter + what facilities they use underneath. In this program, they use the Linux + system libraries. + + */ + +#if defined(LINUX) + +#include <sys/types.h> +#include <sys/socket.h> +#include <sys/param.h> +#include <sys/time.h> +#include <sys/select.h> +#include <netinet/in.h> +#include <netinet/tcp.h> +#include <arpa/inet.h> +#include <netdb.h> +#include <stdio.h> +#include <unistd.h> +#include <errno.h> +#include <fcntl.h> + +#include <stdlib.h> +#include <string.h> +#include <signal.h> + +#include "MQTTClient.h" +#include "FP.cpp" + +#define DEFAULT_STACK_SIZE -1 + + +class IPStack +{ +public: + IPStack() + { + + } + + int Socket_error(const char* aString) + { + + if (errno != EINTR && errno != EAGAIN && errno != EINPROGRESS && errno != EWOULDBLOCK) + { + if (strcmp(aString, "shutdown") != 0 || (errno != ENOTCONN && errno != ECONNRESET)) + printf("Socket error %s in %s for socket %d\n", strerror(errno), aString, mysock); + } + return errno; + } + + int connect(const char* hostname, int port) + { + int type = SOCK_STREAM; + struct sockaddr_in address; + int rc = -1; + sa_family_t family = AF_INET; + struct addrinfo *result = NULL; + struct addrinfo hints = {0, AF_UNSPEC, SOCK_STREAM, IPPROTO_TCP, 0, NULL, NULL, NULL}; + + if ((rc = getaddrinfo(hostname, NULL, &hints, &result)) == 0) + { + struct addrinfo* res = result; + + /* prefer ip4 addresses */ + while (res) + { + if (res->ai_family == AF_INET) + { + result = res; + break; + } + res = res->ai_next; + } + + if (result->ai_family == AF_INET) + { + address.sin_port = htons(port); + address.sin_family = family = AF_INET; + address.sin_addr = ((struct sockaddr_in*)(result->ai_addr))->sin_addr; + } + else + rc = -1; + + freeaddrinfo(result); + } + + if (rc == 0) + { + mysock = socket(family, type, 0); + if (mysock != -1) + { + int opt = 1; + + //if (setsockopt(mysock, SOL_SOCKET, SO_NOSIGPIPE, (void*)&opt, sizeof(opt)) != 0) + // printf("Could not set SO_NOSIGPIPE for socket %d", mysock); + + rc = ::connect(mysock, (struct sockaddr*)&address, sizeof(address)); + } + } + + return rc; + } + + int read(char* buffer, int len, int timeout_ms) + { + struct timeval interval = {timeout_ms / 1000, (timeout_ms % 1000) * 1000}; + if (interval.tv_sec < 0 || (interval.tv_sec == 0 && interval.tv_usec <= 0)) + { + interval.tv_sec = 0; + interval.tv_usec = 100; + } + + setsockopt(mysock, SOL_SOCKET, SO_RCVTIMEO, (char *)&interval, sizeof(struct timeval)); + + //printf("reading %d bytes\n", len); + int rc = ::recv(mysock, buffer, (size_t)len, 0); + if (rc == -1) + Socket_error("read"); + //printf("read %d bytes\n", rc); + return rc; + } + + int write(char* buffer, int len, int timeout) + { + struct timeval tv; + + tv.tv_sec = 0; /* 30 Secs Timeout */ + tv.tv_usec = timeout * 1000; // Not init'ing this can cause strange errors + + setsockopt(mysock, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv,sizeof(struct timeval)); + int rc = ::write(mysock, buffer, len); + //printf("write rc %d\n", rc); + return rc; + } + + int disconnect() + { + return ::close(mysock); + } + +private: + + int mysock; + +}; + + +class Countdown +{ +public: + Countdown() + { + + } + + Countdown(int ms) + { + countdown_ms(ms); + } + + + bool expired() + { + struct timeval now, res; + gettimeofday(&now, NULL); + timersub(&end_time, &now, &res); + //printf("left %d ms\n", (res.tv_sec < 0) ? 0 : res.tv_sec * 1000 + res.tv_usec / 1000); + //if (res.tv_sec > 0 || res.tv_usec > 0) + // printf("expired %d %d\n", res.tv_sec, res.tv_usec); + return res.tv_sec < 0 || (res.tv_sec == 0 && res.tv_usec <= 0); + } + + + void countdown_ms(int ms) + { + struct timeval now; + gettimeofday(&now, NULL); + struct timeval interval = {ms / 1000, (ms % 1000) * 1000}; + //printf("interval %d %d\n", interval.tv_sec, interval.tv_usec); + timeradd(&now, &interval, &end_time); + } + + + void countdown(int seconds) + { + struct timeval now; + gettimeofday(&now, NULL); + struct timeval interval = {seconds, 0}; + timeradd(&now, &interval, &end_time); + } + + + int left_ms() + { + struct timeval now, res; + gettimeofday(&now, NULL); + timersub(&end_time, &now, &res); + //printf("left %d ms\n", (res.tv_sec < 0) ? 0 : res.tv_sec * 1000 + res.tv_usec / 1000); + return (res.tv_sec < 0) ? 0 : res.tv_sec * 1000 + res.tv_usec / 1000; + } + +private: + + struct timeval end_time; +}; + + +int arrivedcount = 0; + +void messageArrived(MQTT::Message* message) +{ + printf("Message %d arrived: qos %d, retained %d, dup %d, packetid %d\n", + ++arrivedcount, message->qos, message->retained, message->dup, message->id); + printf("Payload %.*s\n", message->payloadlen, (char*)message->payload); +} + + +int connect(MQTT::Client<IPStack, Countdown>::connectionLostInfo* info) +{ + const char* hostname = "localhost"; //"m2m.eclipse.org"; + int port = 1883; + printf("Connecting to %s:%d\n", hostname, port); + int rc = info->network->connect(hostname, port); + if (rc != 0) + printf("rc from TCP connect is %d\n", rc); + + MQTTPacket_connectData data = MQTTPacket_connectData_initializer; + data.MQTTVersion = 3; + data.clientID.cstring = (char*)"mbed-icraggs"; + rc = info->client->connect(&data); + if (rc != 0) + printf("rc from MQTT connect is %d\n", rc); + + return rc; +} + + +int main(int argc, char* argv[]) +{ + IPStack ipstack = IPStack(); + float version = 0.3; + const char* topic = "mbed-sample"; + + printf("Version is %f\n", version); + + MQTT::Client<IPStack, Countdown> client = MQTT::Client<IPStack, Countdown>(ipstack); + + client.setConnectionLostHandler(connect); + + MQTT::Client<IPStack, Countdown>::connectionLostInfo info = {&client, &ipstack}; + int rc = connect(&info); + + rc = client.subscribe(topic, MQTT::QOS2, messageArrived); + if (rc != 0) + printf("rc from MQTT subscribe is %d\n", rc); + + MQTT::Message message; + + // QoS 0 + char buf[100]; + sprintf(buf, "Hello World! QoS 0 message from app version %f", version); + message.qos = MQTT::QOS0; + message.retained = false; + message.dup = false; + message.payload = (void*)buf; + message.payloadlen = strlen(buf)+1; + rc = client.publish(topic, &message); + while (arrivedcount == 0) + client.yield(100); + + // QoS 1 + printf("Now QoS 1\n"); + sprintf(buf, "Hello World! QoS 1 message from app version %f", version); + message.qos = MQTT::QOS1; + message.payloadlen = strlen(buf)+1; + rc = client.publish(topic, &message); + while (arrivedcount == 1) + client.yield(100); + + // QoS 2 + sprintf(buf, "Hello World! QoS 2 message from app version %f", version); + message.qos = MQTT::QOS2; + message.payloadlen = strlen(buf)+1; + rc = client.publish(topic, &message); + while (arrivedcount == 2) + client.yield(100); + + rc = client.unsubscribe(topic); + if (rc != 0) + printf("rc from unsubscribe was %d\n", rc); + + rc = client.disconnect(); + if (rc != 0) + printf("rc from disconnect was %d\n", rc); + + ipstack.disconnect(); + + printf("Finishing with %d messages received\n", arrivedcount); + + return 0; +} + +#endif