linux 新闻文章订阅地址

Linux C MQTT订阅是指在Linux操作系统下使用C语言编写的程序，通过MQTT协议进行消息订阅的过程。MQTT（Message Queuing Telemetry Transport）是一种轻量级的消息传输协议，常用于物联网设备之间的通信。 在Linux C中进行MQTT订阅，需要使用MQTT的C语言库，例如Eclipse Paho或者Mosquitto等。以下是一个简单的Linux C MQTT订阅的示例代码： ```c #include <stdio.h> #include <stdlib.h> #include <string.h> #include <MQTTClient.h> #define ADDRESS "tcp://mqtt.eclipse.org:1883" #define CLIENTID "ExampleClientSub" #define TOPIC "example/topic" #define QOS 1 #define TIMEOUT 10000L volatile MQTTClient_deliveryToken deliveredtoken; int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message) { printf("Message arrived on topic: %s\n", topicName); printf("Message: %.*s\n", message->payloadlen, (char*)message->payload); MQTTClient_freeMessage(&message); MQTTClient_free(topicName); return 1; } void delivered(void *context, MQTTClient_deliveryToken dt) { printf("Message with token value %d delivery confirmed\n", dt); deliveredtoken = dt; } int main(int argc, char* argv[]) { MQTTClient client; MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer; int rc; MQTTClient_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL); conn_opts.keepAliveInterval = 20; conn_opts.cleansession = 1; MQTTClient_setCallbacks(client, NULL, NULL, msgarrvd, delivered); if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS) { printf("Failed to connect, return code %d\n", rc); exit(EXIT_FAILURE); } MQTTClient_subscribe(client, TOPIC, QOS); printf("Subscribed to topic: %s\n", TOPIC); while (1) { // 这里可以添加其他逻辑代码 } MQTTClient_disconnect(client, 10000); MQTTClient_destroy(&client); return rc; } ``` 上述示例代码使用了Eclipse Paho的C语言库，通过连接到指定的MQTT服务器（例如mqtt.eclipse.org），订阅了名为"example/topic"的主题。当有消息到达时，会调用msgarrvd函数进行处理。