https://blog.csdn.net/dancer__sky/article/details/77855249#comments
概述:工作之余学习mqtt,使用开源的Mosquitto实现mqtt的使用。如:broker(服务器/代理),消息订阅及发布。
系统环境:ubuntu14.04
1,MQTT简介
MQTT 是一个轻量级协议,使用基于 TCP/IP 协议的发布/订阅消息转发模式,在物联网应用中大规模使用。 MQTT 协议的中心是 broker( 服务器/代理) ,客户端通过订阅消息和发布消息进行数据交互 ,如下图所示:
2,Mosquitto安装
(1)mosquitto下载
下载地址,进入下载页面,选择source中第一个下载mosquitto-1.4.9.tar.gz
(2)mosquitto依赖库安装$ sudo apt-get install libssl-dev $ sudo apt-get install libc-ares-dev $ sudo apt-get install uuid-dev
(3)mosquitto的安装//解压 $ tar zxvf mosquitto-1.4.9.tar.gz $ cd mosquitto-1.4.9 $ make $ sudo make install
(4)编译问题解决
如果出现error while loading shared libraries: libmosquitto.so.1: cannot open shared object file: No such file or directory//创建链接 $ sudo ln -s /usr/local/lib/libmosquitto.so.1 /usr/lib/libmosquitto.so.1 //更新链接 $ sudo ldconfig
3,mosquitto使用
进入命令行界面
(1)启动mosquitto服务器$ mosquitto -v
(2)订阅消息(如topic)$ mosquitto_sub -v -t topic
(3)发布消息$ mosquitto_pub -t topic -m good
效果如下图所示:
4,libmosquitto客户端编程(发布消息,订阅消息)
在安装mosquitto成功后,可以在/usr/local/lib文件夹中有libmosquitto.so.1等文件,如下图所示:
这里贴一个demo
客户端(订阅消息)#include #include #include #include #define HOST "localhost" #define PORT 1883 #define KEEP_ALIVE 60 bool session = true; void my_message_callback(struct mosquitto *mosq, void *userdata, const struct mosquitto_message *message) { if(message->payloadlen){ printf("%s %s", message->topic, message->payload); }else{ printf("%s (null)\n", message->topic); } fflush(stdout); } void my_connect_callback(struct mosquitto *mosq, void *userdata, int result) { int i; if(!result){ /* Subscribe to broker information topics on successful connect. */ mosquitto_subscribe(mosq, NULL, "Gai爷:", 2); }else{ fprintf(stderr, "Connect failed\n"); } } void my_subscribe_callback(struct mosquitto *mosq, void *userdata, int mid, int qos_count, const int *granted_qos) { int i; printf("Subscribed (mid: %d): %d", mid, granted_qos[0]); for(i=1; i<qos_count; i++){ printf(", %d", granted_qos[i]);="" }="" printf("\n");="" }="" void my_log_callback(struct mosquitto *mosq, void *userdata, int level, const char *str)="" {="" ="" * pring all log messages regardless of level. *="" printf("%s\n", str);="" int main()="" struct mosquitto *mosq =" NULL;" libmosquitto 库初始化="" mosquitto_lib_init();="" 创建mosquitto客户端="" mosq =" mosquitto_new(NULL,session,NULL);" if(!mosq){="" printf("create client failed..\n");="" mosquitto_lib_cleanup();="" return 1;="" 设置回调函数,需要时可使用="" mosquitto_log_callback_set(mosq, my_log_callback);="" mosquitto_connect_callback_set(mosq, my_connect_callback);="" mosquitto_message_callback_set(mosq, my_message_callback);="" mosquitto_subscribe_callback_set(mosq, my_subscribe_callback);="" 客户端连接服务器="" if(mosquitto_connect(mosq, host, port, keep_alive)){="" fprintf(stderr, "unable to connect.\n");="" 循环处理网络消息="" mosquitto_loop_forever(mosq, -1, 1);="" mosquitto_destroy(mosq);="" mosquitto_lib_cleanup();="" return 0;="" }
客户端(发布消息)#include #include #include #include #define HOST "localhost" #define PORT 1883 #define KEEP_ALIVE 60 #define MSG_MAX_SIZE 512 bool session = true; int main() { char buff[MSG_MAX_SIZE]; struct mosquitto *mosq = NULL; //libmosquitto 库初始化 mosquitto_lib_init(); //创建mosquitto客户端 mosq = mosquitto_new(NULL,session,NULL); if(!mosq){ printf("create client failed..\n"); mosquitto_lib_cleanup(); return 1; } //连接服务器 if(mosquitto_connect(mosq, HOST, PORT, KEEP_ALIVE)){ fprintf(stderr, "Unable to connect.\n"); return 1; } //开启一个线程,在线程里不停的调用 mosquitto_loop() 来处理网络信息 int loop = mosquitto_loop_start(mosq); if(loop != MOSQ_ERR_SUCCESS) { printf("mosquitto loop error\n"); return 1; } while(fgets(buff, MSG_MAX_SIZE, stdin) != NULL) { /*发布消息*/ mosquitto_publish(mosq,NULL,"Gai爷:",strlen(buff)+1,buff,0,0); memset(buff,0,sizeof(buff)); } mosquitto_destroy(mosq); mosquitto_lib_cleanup(); return 0; }
注意
在编译程序时需加上-lmosquitto链接。如:$ gcc -o mosquitto_client_sub mosquitto_client_sub.c -lmosquitto
5,客户端使用
(1)开启mosquitto服务$ mosquitto -v
(2)启动订阅消息客户端及发布消息客户端$ ./mosquitto_client_sub $ ./mosquitto_client_pub
(3)效果
参考资料:
如果想详细了解mqtt中libmosquitto的使用可以看一下这篇文章。
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