linux C语言实现mqtt带密码的连接

要在Linux上使用C语言实现MQTT带密码的连接，你可以使用Paho MQTT C库。以下是实现的步骤：

1. 下载和安装Paho MQTT C库

你可以从Eclipse Paho网站下载最新版本的Paho MQTT C库，按照说明进行安装和编译。

2. 设置连接参数

在你的C代码中，需要设置连接参数，包括MQTT服务器的IP地址、端口号、客户端ID、用户名和密码等。

char *host = "mqtt.yourserver.com";
int port = 1883;
char *client_id = "your_client_id";
char *username = "your_username";
char *password = "your_password";

3. 创建MQTT客户端

使用Paho MQTT C库创建MQTT客户端，并设置连接参数。

MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;

MQTTClient_create(&client, host, client_id, MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.username = username;
conn_opts.password = password;
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;

4. 连接MQTT服务器

使用MQTT客户端连接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);
}

5. 发布和订阅MQTT主题

使用MQTT客户端发布和订阅MQTT主题。

char *topic = "your_topic";
int qos = 1;
pubmsg.qos = qos;
pubmsg.retained = 0;
while (1) {
    pubmsg.payload = "Hello world!";
    pubmsg.payloadlen = strlen("Hello world!");
    MQTTClient_publishMessage(client, topic, &pubmsg, &token);
    printf("Waiting for up to %d seconds for publication of %s\n"
           "on topic %s for client with ClientID: %s\n",
           (int)(TIMEOUT/1000), payload, topic, client_id);
    rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
    printf("Message with delivery token %d delivered\n", token);
    sleep(1);
}

6. 断开MQTT连接

使用MQTT客户端断开MQTT连接。

MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);

注意：在实际使用中，你需要正确设置连接参数、主题和消息内容等，以满足你的需求。