paho mqtt c 发布

好的，以下是使用paho mqtt c发布MQTT消息的基本步骤：

1. 首先，您需要安装paho mqtt c库：

sudo apt-get install libssl-dev
sudo apt-get install libpaho-mqtt-dev

2. 然后，您需要编写C代码来实现MQTT发布。以下是一个简单的代码示例，用于发布主题为“test”的MQTT消息：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <MQTTClient.h>

#define ADDRESS     "tcp://localhost:1883"
#define CLIENTID    "ExampleClientPub"
#define TOPIC       "test"
#define QOS         1
#define TIMEOUT     10000L

int main(int argc, char* argv[]) {
    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient_message pubmsg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;
    int rc;

    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;

    MQTTClient_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
    rc = MQTTClient_connect(client, &conn_opts);
    if (rc != MQTTCLIENT_SUCCESS) {
        printf("Failed to connect, return code %d\n", rc);
        exit(-1);
    }

    pubmsg.payload = "Hello MQTT";
    pubmsg.payloadlen = strlen(pubmsg.payload);
    pubmsg.qos = QOS;
    pubmsg.retained = 0;
    MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
    printf("Waiting for publication of %s\n"
           "on topic %s for client with ClientID: %s\n",
           "Hello MQTT", TOPIC, CLIENTID);
    rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
    printf("Message with delivery token %d delivered\n", token);
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);
    return rc;
}

3. 编译并运行代码，您现在应该能够成功发布消息到名为“test”的MQTT主题。

请注意，这只是一个简单的示例，您需要根据您的需求进行适当的修改。同时，请确保您已经正确配置了MQTT代理服务器的连接信息。