Eclipse Paho：MQTT Client C的使用

https://www.eclipse.org/paho/downloads.php

eclipse/paho.mqtt.c库（使用v1.3.0）的下载地址是：https://github.com/eclipse/paho.mqtt.c/tree/v1.3.0

1、paho.mqtt.c-1.3.0\CMakeLists.txt，使能PAHO_BUILD_STATIC 和PAHO_BUILD_SAMPLES 

## build options
SET(PAHO_WITH_SSL FALSE CACHE BOOL "Flag that defines whether to build ssl-enabled binaries too. ")
SET(PAHO_BUILD_STATIC TRUE CACHE BOOL "Build static library") #firecat modify
SET(PAHO_BUILD_DOCUMENTATION FALSE CACHE BOOL "Create and install the HTML based API documentation (requires Doxygen)")
SET(PAHO_BUILD_SAMPLES TRUE CACHE BOOL "Build sample programs") #firecat modify
SET(PAHO_BUILD_DEB_PACKAGE FALSE CACHE BOOL "Build debian package")
SET(PAHO_ENABLE_TESTING TRUE CACHE BOOL "Build tests and run")
SET(PAHO_ENABLE_CPACK TRUE CACHE BOOL "Enable CPack")

 

2、paho.mqtt.c-1.3.0\src\samples\CMakeLists.txt

#*******************************************************************************
#  Copyright (c) 2015, 2017 logi.cals GmbH 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
#  and the Eclipse Distribution License is available at
#    http://www.eclipse.org/org/documents/edl-v10.php.
#
#  Contributors:
#     Rainer Poisel - initial version
#     Ian Craggs - update sample names
#*******************************************************************************/

# Note: on OS X you should install XCode and the associated command-line tools

## compilation/linkage settings
INCLUDE_DIRECTORIES(
    .
    ${CMAKE_SOURCE_DIR}/src
    ${CMAKE_BINARY_DIR}
    )

IF (WIN32)
  	ADD_DEFINITIONS(/DCMAKE_BUILD /D_CRT_SECURE_NO_DEPRECATE)
ENDIF()

# sample files c
#ADD_EXECUTABLE(paho_c_pub paho_c_pub.c pubsub_opts.c) #firecat
#ADD_EXECUTABLE(paho_c_sub paho_c_sub.c pubsub_opts.c)
#ADD_EXECUTABLE(paho_cs_pub paho_cs_pub.c pubsub_opts.c)
#ADD_EXECUTABLE(paho_cs_sub paho_cs_sub.c pubsub_opts.c)

#TARGET_LINK_LIBRARIES(paho_c_pub paho-mqtt3as)
#TARGET_LINK_LIBRARIES(paho_c_sub paho-mqtt3as)
#TARGET_LINK_LIBRARIES(paho_cs_pub paho-mqtt3cs)
#TARGET_LINK_LIBRARIES(paho_cs_sub paho-mqtt3cs)

ADD_EXECUTABLE(MQTTAsync_subscribe MQTTAsync_subscribe.c)
ADD_EXECUTABLE(MQTTAsync_publish MQTTAsync_publish.c)
ADD_EXECUTABLE(MQTTClient_subscribe MQTTClient_subscribe.c)
ADD_EXECUTABLE(MQTTClient_publish MQTTClient_publish.c)
ADD_EXECUTABLE(MQTTClient_publish_async MQTTClient_publish_async.c)

TARGET_LINK_LIBRARIES(MQTTAsync_subscribe paho-mqtt3a)
TARGET_LINK_LIBRARIES(MQTTAsync_publish paho-mqtt3a)
TARGET_LINK_LIBRARIES(MQTTClient_subscribe paho-mqtt3c)
TARGET_LINK_LIBRARIES(MQTTClient_publish paho-mqtt3c)
TARGET_LINK_LIBRARIES(MQTTClient_publish_async paho-mqtt3c)

#INSTALL(TARGETS paho_c_sub #firecat
#                paho_c_pub
#                paho_cs_sub
#                paho_cs_pub
#                MQTTAsync_subscribe
#                MQTTAsync_publish
#                MQTTClient_subscribe
#                MQTTClient_publish
#                MQTTClient_publish_async

#    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
#    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

 

3、使用cmake release编译，生成以下的动态库和静态库文件：

The Paho C client comprises four shared libraries:

libmqttv3a.so - asynchronous
libmqttv3as.so - asynchronous with SSL
libmqttv3c.so - "classic" / synchronous
libmqttv3cs.so - "classic" / synchronous with SSL
Optionally, using the CMake build, you can build static versions of those libraries.

libpaho-mqtt3a.so

libpaho-mqtt3a.so.1

libpaho-mqtt3a.so.1.3.0

libpaho-mqtt3a-static.a

libpaho-mqtt3c.so

libpaho-mqtt3c.so.1

libpaho-mqtt3c.so.1.3.0

libpaho-mqtt3c-static.a

把它们一起拷贝到路径：/usr/local/lib/

此时需要在/etc/ld.so.conf中加入库文件所在的目录:/usr/local/lib/

然后在终端执行命令，使之生效:

[root@localhost etc]# ldconfig

注意，/usr/local/lib/每次有库文件更新，都需要终端重新运行一次ldconfig这条命令。

 

4、使用案例

/*******************************************************************************
 * Copyright (c) 2012, 2017 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 contribution
 *******************************************************************************/

#include 
#include 
#include 
#include "MQTTClient.h"

#include 
#include 
#include 
#include     /*setrlimit */
#include  //daemonize

#define ADDRESS     "tcp://192.168.83.128:1883"
#define CLIENTID    "id001"
#define TOPIC       "keepalived"
#define PAYLOAD     "Hello World!"
#define QOS         0
#define USERNAME    "inTerm"
#define PASSWORD    "in2018"

static int run = 1;

volatile MQTTClient_deliveryToken deliveredtoken;

void daemonize(void) { //come from /redis/server.c/daemonize()
    int fd;

    if (fork() != 0) exit(0); /* parent exits */
    setsid(); /* create a new session */

    /* Every output goes to /dev/null. If Redis is daemonized but
     * the 'logfile' is set to 'stdout' in the configuration file
     * it will not log at all. */
    if ((fd = open("/dev/null", O_RDWR, 0)) != -1) {
        dup2(fd, STDIN_FILENO);
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        if (fd > STDERR_FILENO) close(fd);
    }
}

void signal_exit_func(int signo)
{
    run = 0;
    printf("exit signo is %d\n", signo);
}

void signal_exit_handler()
{
    struct sigaction sa;
    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = signal_exit_func;
    sigaction(SIGINT, &sa, NULL);//当按下ctrl+c时，它的效果就是发送SIGINT信号
    sigaction(SIGTERM, &sa, NULL);//kill pid
    sigaction(SIGQUIT, &sa, NULL);//ctrl+\代表退出SIGQUIT

    //SIGSTOP和SIGKILL信号是不可捕获的,所以下面两句话写了等于没有写
    sigaction(SIGKILL, &sa, NULL);//kill -9 pid
    sigaction(SIGSTOP, &sa, NULL);//ctrl+z代表停止

    //#define    SIGTERM        15
    //#define    SIGKILL        9
    //kill和kill -9，两个命令在linux中都有杀死进程的效果，然而两命令的执行过程却大有不同，在程序中如果用错了，可能会造成莫名其妙的现象。
    //执行kill pid命令，系统会发送一个SIGTERM信号给对应的程序。
    //执行kill -9 pid命令，系统给对应程序发送的信号是SIGKILL，即exit。exit信号不会被系统阻塞，所以kill -9能顺利杀掉进程。
}

void delivered(void *context, MQTTClient_deliveryToken dt)
{
    printf("Message with token value %d delivery confirmed\n", dt);
    deliveredtoken = dt;
}

int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
    int i;
    char* payloadptr;

    printf("Message arrived\n");
    printf("     topic: %s\n", topicName);
    printf("   message: ");

    payloadptr = message->payload;
    for(i=0; ipayloadlen; i++)
    {
        putchar(*payloadptr++);
    }
    putchar('\n');
    MQTTClient_freeMessage(&message);
    MQTTClient_free(topicName);
    return 1;
}

void connlost(void *context, char *cause)//心跳时间达到，如果没有收到服务器的reponse，客户端的socket会自动关闭
{
    printf("\nConnection lost\n");
    printf("     cause: %s\n", cause);
    exit(EXIT_FAILURE); //firecat
}

//./MQTTClient_firecat "tcp://192.168.83.128:1883" "id001"
int main(int argc, char* argv[])
{
    int background = 1;//firecat add
    if (background)
    {
        daemonize();
    }

    //signal(SIGHUP, SIG_IGN); //开启的话，就捕获不到终端窗口关闭的信号了。即窗口关闭，进程仍然进行。
    signal(SIGPIPE, SIG_IGN);

    char *serverURI;
    char *clientId;
    if (argc == 1)
    {
        serverURI = ADDRESS;
        clientId = CLIENTID;
    }
    else if (argc == 3)
    {
        serverURI = argv[1];
        clientId = argv[2];
    }
    else
    {
        printf("argc error\n");
        exit(EXIT_FAILURE);
    }

    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    int rc;
    int ch;

    MQTTClient_create(&client, serverURI, clientId,
                      MQTTCLIENT_PERSISTENCE_NONE, NULL);
    conn_opts.keepAliveInterval = 60;
    conn_opts.cleansession = 1;
    conn_opts.MQTTVersion = MQTTVERSION_3_1_1;
    conn_opts.username = USERNAME;
    conn_opts.password = PASSWORD;

    MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered);

    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        printf("Failed to connect, return code %d\n", rc);
        exit(EXIT_FAILURE);
    }
    printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
           "Press Q to quit\n\n", TOPIC, CLIENTID, QOS);
    MQTTClient_subscribe(client, TOPIC, QOS);

    if (background)
    {
        while (run)
        {
            sleep(1);
        }
    }
    else
    {
        do
        {
            ch = getchar();
        } while(ch!='Q' && ch != 'q');
    }

    MQTTClient_unsubscribe(client, TOPIC);
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);
    return rc;
}