Linux C的MQTT测试代码编写 - 跨主机的MQTT客户端通信

Posted 2021-09-05 Andrea-地面宇航员

Linux C的MQTT测试代码编写

做完在同一个主机下的MQTT客户端实验后，做亿点点改变，我们使用移植好的MQTT接口在Ubuntu下写一个MQTT的客户端，然后和windows下的MQTT.fx工具通信。

1. 代码

   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #include "MQTTClient.h"  //需要在系统中提前安装好MQTT，可以参考
   #define ADDRESS "tcp://192.168.50.81:1883" //根据 MQTT 实际主机地址调整
   #define CLIENTID_PUB "ExampleClientPub"
   #define CLIENTID_SUB "ExampleClientSub"
   #define QOS 1
   #define TIMEOUT 10000L
   #define PUB_TOPIC "ScratchToSoftWare" 
   #define SUB_TOPIC "SoftWareToScratch" 
   #define NUM_THREADS 2    		  //线程个数，一个用于发布，一个用于订阅
   #define FAN_OFF "{'fan':false}"   //表示风扇关闭的json字符串
   #define FAN_ON "{'fan':true}"     //表示风扇打开的json字符串 
   int fan_state = 0; 
   volatile MQTTClient_deliveryToken deliveredtoken;
   
   
   //传递给MQTTClient_setCallbacks的回调函数，消息发送成功后，调用此回调函数
   void delivered(void *context, MQTTClient_deliveryToken dt)
   {
   	printf("Message with token value %d delivery confirmed\\n", dt);
   	deliveredtoken = dt;
   }
   
   //传递给MQTTClient_setCallbacks的回调函数 消息到达后，调用此回调函数 
   int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
   {
   	printf("Message arrived\\n");
   	printf(" topic: %s\\n", topicName);
   	printf(" message: %.*s\\n", message->payloadlen, (char*)message->payload);
   	MQTTClient_freeMessage(&message);
   	MQTTClient_free(topicName);
   	return 1; 
   }
   
   //传递给MQTTClient_setCallbacks的回调函数 连接异常断开后调用此回调函数 
   void connlost(void *context, char *cause)
   {
   	printf("\\nConnection lost\\n");
   	printf(" cause: %s\\n", cause);
   }
   
   //实现MQTT的订阅 
   void *mqtt_subscribe()
   {
   	MQTTClient client;  //定义一个MQTT客户端client
   	MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
   	int rc;
   	//初始化client，设置MQTT服务器的地址"tcp://192.168.50.81:1883" 并订阅"ExampleClientSub"
   	if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID_SUB,
   					MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
   	{
   		printf("Failed to create client, return code %d\\n", rc);
   		rc = EXIT_FAILURE;
   		goto exit;
   	}
   	//设置回调函数，
   	if ((rc = MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd,
   					delivered)) != MQTTCLIENT_SUCCESS)
   	{
   		printf("Failed to set callbacks, return code %d\\n", rc);
   		rc = EXIT_FAILURE;
   		goto destroy_exit;
   	}
   	conn_opts.keepAliveInterval = 20;
   	conn_opts.cleansession = 1;
   	//连接服务器
   	if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
   	{
   		printf("Failed to connect, return code %d\\n", rc);
   		rc = EXIT_FAILURE;
   		goto destroy_exit;
   	}
   	printf("Subscribing to topic %s\\nfor client %s using QoS%d\\n\\n"
   			"Press Q<Enter> to quit\\n\\n", SUB_TOPIC, CLIENTID_SUB, QOS);
   
   	//订阅主题 
   	if ((rc = MQTTClient_subscribe(client, SUB_TOPIC, QOS)) != MQTTCLIENT_SUCCESS)
   	{
   		printf("Failed to subscribe, return code %d\\n", rc);
   		rc = EXIT_FAILURE;
   	}
   	else
   	{
   		int ch;
   		do
   		{
   			ch = getchar();
   		} while (ch!='Q' && ch != 'q');  //等待输入字符 'Q'或'q'
   		if ((rc = MQTTClient_unsubscribe(client, SUB_TOPIC)) != MQTTCLIENT_SUCCESS)  	//取消订阅 
   		{
   			printf("Failed to unsubscribe, return code %d\\n", rc);
   			rc = EXIT_FAILURE;
   		} }
   	if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)  //断开和服务器的连接 
   	{
   		printf("Failed to disconnect, return code %d\\n", rc);
   		rc = EXIT_FAILURE;
   	}
   destroy_exit:
   	MQTTClient_destroy(&client); //释放客户端的资源 
   exit:
   	return NULL; 
   }
   
   //实现MQTT的发布 
   void *mqtt_publish()
   {
   	MQTTClient client;  //定义一个MQTT客户端 
   	MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
   	MQTTClient_message pubmsg = MQTTClient_message_initializer;
   	MQTTClient_deliveryToken token;
   	char data[1024];
   	int rc;
   	//初始化MQTT客户端 
   	if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID_PUB,
   					MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
   	{
   		printf("Failed to create client, return code %d\\n", rc);
   		exit(EXIT_FAILURE);
   	}
   	conn_opts.keepAliveInterval = 20;
   	conn_opts.cleansession = 1;
   	//连接MQTT服务器 
   	if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
   	{
   		printf("Failed to connect, return code %d\\n", rc);
   		exit(EXIT_FAILURE);
   	}
   	pubmsg.qos = QOS;
   	pubmsg.retained = 0;
   	while(1) {
   		//判断风扇标志位的值，封装发送的消息
   		if (fan_state == 0) {
   			pubmsg.payload = FAN_ON;
   			pubmsg.payloadlen = strlen(FAN_ON);
   			fan_state = 1; } else {
   				pubmsg.payload = FAN_OFF;
   				pubmsg.payloadlen = strlen(FAN_OFF);
   				fan_state = 0; }
   		//循环发送消息，在"ScratchToSoftWare" 这个主题下发布消息
   		if ((rc = MQTTClient_publishMessage(client, PUB_TOPIC,
   						&pubmsg, &token)) != MQTTCLIENT_SUCCESS)
   		{
   			printf("Failed to publish message, return code %d\\n", rc);
   			exit(EXIT_FAILURE);
   		}
   		printf("Waiting for up to %d seconds for publication of %s\\n"
   				"on topic %s for client with ClientID: %s\\n", (int)(TIMEOUT/1000), data, PUB_TOPIC, CLIENTID_PUB);
   		rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
   		printf("Message with delivery token %d delivered\\n", token);
   		usleep(5000000);
   	}
   	if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)
   		printf("Failed to disconnect, return code %d\\n", rc);
   	MQTTClient_destroy(&client);
   	return NULL; 
   }
   
   
   int main(int argc, char **argv)
   {
   	pthread_t threads[NUM_THREADS];
   	pthread_create(&threads[0], 0, mqtt_subscribe, NULL);
   	pthread_create(&threads[1], 0, mqtt_publish, NULL);
   	pause();
   	return 0; 
   }
   
   

2. 编译命令

   $gcc main.c -lpthread -lpaho-mqtt3c
   

3. 效果展示