如何使用 Paho C 库连接到 HiveMQ 代理

Question

我在HiveMq云中创建了一个hiveMQ集群，并创建了用户名和密码。

我从 Paho C 库创建 MQTTClient_connectOptions 并将我的用户名和密码作为参数：

#define ADDRESS     "myURL:8883"  // broker address for use in local machine 
#define CLIENTID    "myclientID"
#define TOPIC  "testtopic"
#define TIMEOUT     10000L   // ms
#define USERNAME "myUsername"
#define PASSWORD "myPassword" 

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

    int rc; //status code received from broker
    rc = MQTTClient_create(&client, ADDRESS, CLIENTID,
                            MQTTCLIENT_PERSISTENCE_NONE, NULL);
    printf("Client create reason code: %d\n", rc);
    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.username = USERNAME;
    conn_opts.password = PASSWORD;
    

    MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered);

    // checks whether the connection is successful or not
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        printf("Failed to connect, return code %d\n", (MQTTClient_connect(client, &conn_opts)));
        exit(-1);
    }

    MQTTClient_message msg = MQTTClient_message_initializer;
    
    /*
        sending data
        pass sensor data to this function for publishing
    */
    rc = publish_message(client, TOPIC, msg, &token, "4561237891", "23.6", "170.3", "524.08");

    // Disconnect
    int timeout = 100;  //second
    MQTTClient_disconnect(client, timeout);
    MQTTClient_destroy(&client);

    return rc;
}

MQTTClient_connect 无法连接到代理并且 return -1:

Failed to connect, return code -1

我尝试使用 MQTT CLI 连接，它成功了，我发布并订阅了一个主题并传输了一条消息。所以我的身份验证是错误的。

如何使用 Paho C 库正确连接简单身份验证？

Answer 1

ADDRESS 应该是 URI，而不仅仅是 host:port 组合。

因此您需要在 host:port

之前包含 tcp:// 或 ssl://

例如ssl://5xxxxxxxxxxxxxxxxxxxxxxxxx7bcac5.env-1.hivemq.cloud:8883

来自 Paho C 客户端 doc:

Parameters

handle -- A pointer to an MQTTClient handle. The handle is populated with a valid client reference following a successful return from this function.

serverURI -- A null-terminated string specifying the server to which the client will connect. It takes the form protocol://host:port. Currently, protocol must be tcp or ssl. For host, you can specify either an IP address or a host name. For instance, to connect to a server running on the local machines with the default MQTT port, specify tcp://localhost:1883.

Answer 2

正如@hardillb 所写，您需要使用 TLS 连接到 HiveMQ Cloud。

您可以通过连接到 ssl://<your-address>:<your-port> 并通过将 MQTTClient_SSLOptions 添加到您的 MQTTClient_connectOptions 来为客户端启用它来做到这一点。

MQTTClient_SSLOptions ssl_opts = MQTTClient_SSLOptions_initializer;
ssl_opts.enableServerCertAuth = 0;
conn_opts.ssl = &ssl_opts;

来源：https://www.hivemq.com/blog/mqtt-client-library-pahocclient/

您需要带有 s 的变体（例如 paho-mqtt3cs）以支持 SSL/TLS。

命令行工具的源码中也使用了这个： https://github.com/eclipse/paho.mqtt.c/blob/master/src/samples/paho_cs_pub.c

github 自述文件还展示了如何构建它（如果需要）： https://github.com/eclipse/paho.mqtt.c/blob/master/README.md

如何使用 Paho C 库连接到 HiveMQ 代理

How to connect to HiveMQ broker with Paho C library

c

mqtt

hivemq

paho