MQTT无法连接到后端AWS IoT核心

Question

更新:我正在尝试连接一个后端(亚马逊网络服务IoT核心)，因为我正在使用一个运行busybox镜像的小型wp77。当使用8883端口时，连接超时，因此我已更改为端口443，并且我可以连接到后端，但是，套接字在三次尝试后关闭。这是我的应用程序中的日志读数：

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttMain2717 | DSC ...正在启动MQTT连接

Aug 14 03:29:13 fx30s user.info Legato:信息| mqttMain2717 |

Aug 14 03:29:13 fx30s user.info Legato:信息| mqttMain2717 |

Aug 14 03:29:13 fx30s user.info T=main : INFO | mqttMain2717/mqttCliSvrComponent | mqttCliSvr.c DcsStateHandler() 317 | rmnet_data0 connected！启动MQTT会话

Aug 14 03:29:13 fx30s user.info T=main : INFO | mqttClient1120/mqttClientApiComponent mqttClient_StartSession| mqttClientApi.c mqttClient_StartSession() 452 | StartSession已调用

Aug 14 03:29:13 fx30s user.info T=main : INFO | mqttClient1120/mqttClientApiComponent mqttClient_StartSession| mqttClientApi.c mqttClient_StartSession() 455 | mqttClientPts NOT NULL

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 | mqtt_StartSession...正在连接...

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 |。播种随机数生成器...好的

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 |。正在加载CA根证书...从证书加载证书ok (跳过0)

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 |。正在加载客户端证书.../home/root/aws-iot/xxxxxx-certificate.pem.crt ok

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 |。正在加载客户端私钥.../home/root/aws-iot/xxxxxx-private.pem.key ok

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 |。正在连接到tcp/xxxxxx-ats.iot.ap-southeast-1.amazonaws.com/443...

Aug 14 03:29:13 fx30s user.info Legato:信息| mqttClient1120 | ok

Aug 14 03:29:13 fx30s user.info Legato: INFO | mqttClient1120 |。正在设置TLS结构...好的

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |。正在执行TLS握手...好的

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |协议为TLSv1.2

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |密码套件is TLS-ECDHE-RSA-WITH-AES-128-GCM-SHA256

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |。正在验证对等X.509证书...好的

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 | clientId : FX30S

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 | username：

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |正在尝试(1/3)连接到tcp://xxxxxx-ats.iot.ap-southeast-1.amazonaws.com:443...

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |检查连接选项。

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 | MQTT serialize connection。

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 | MQTT发送数据包。

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |发送的字节数: 31

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 |发送的总字节数: 31，共31

Aug 14 03:29:15 fx30s user.info Legato: INFO | mqttClient1120 | MQTT等待CONNACK

Aug 14 03:29:20 fx30s user.info Legato: INFO | mqttClient1120 | MQTT现在正在退出，返回-1

Aug 14 03:29:20 fx30s user.info Legato:信息| mqttClient1120 |失败

Aug 14 03:29:20 fx30s user.info Legato: INFO | mqttClient1120 | tlsSocket_close 1

这是我从github拿来的代码，在我的设备上测试...

int MQTTConnect(Client* c, MQTTPacket_connectData* options)
{
    Timer connect_timer;
    int rc = FAILURE;
    MQTTPacket_connectData default_options = MQTTPacket_connectData_initializer;
    int len = 0;
    
    InitTimer(&connect_timer);
    countdown_ms(&connect_timer, c->command_timeout_ms);

    if (c->isconnected) // don't send connect packet again if we are already connected
        goto exit;

    fprintf(stdout, "Check connection options.");
    fflush(stdout);

    if (options == 0)
    {
        fprintf(stdout, "MQTTConnect Set default options...");
        fflush(stdout);
        options = &default_options; // set default options if none were supplied
    }
    
    c->keepAliveInterval = options->keepAliveInterval;
    countdown(&c->ping_timer, c->keepAliveInterval);
    fprintf(stdout, "MQTT serialize connection.");
    fflush(stdout);
    if ((len = MQTTSerialize_connect(c->buf, c->buf_size, options)) <= )
        goto exit;

    #if 0
    {
        int i;
        for (i=0; i<len; i++)
        {
            fprintf(stdout, "%.2x", c->buf[i]);
        }
        fprintf(stdout, "\n");
        fflush(stdout);

        fprintf(stdout, "\n%.*s\n", len, c->buf);
        fflush(stdout);
    }
    #endif

    fprintf(stdout, "MQTT send packet.");
    fflush(stdout);
    if ((rc = sendPacket(c, len, &connect_timer)) != SUCCESS)  // send the connect packet
        goto exit; // there was a problem
    
    // this will be a blocking call, wait for the connack
    fprintf(stdout, "MQTT waiting for CONNACK");
    fflush(stdout);
    if (waitfor(c, CONNACK, &connect_timer) == CONNACK)
    {
        unsigned char connack_rc = 255;
        char sessionPresent = 0;
        if (MQTTDeserialize_connack((unsigned char*)&sessionPresent, &connack_rc, c->readbuf, c->readbuf_size) == 1)
            rc = connack_rc;
        else
            rc = FAILURE;
    }
    else
        rc = FAILURE;
exit:
    fprintf(stdout, "MQTT is now exiting with %d", rc );
    fflush(stdout);  
    if (rc == SUCCESS)
    //if (SUCCESS == SUCCESS)
        c->isconnected = 1;
    return rc;
    //return SUCCESS;
}

由于某些原因，后端无法使用CONNACK确认连接，这就是此操作失败的原因。AWS指定在通过端口443连接到后端时使用APLN，所以我想知道这是否是问题所在，以及如何在paho.mqtt.c上为tls指定此协议(我知道python有解决方案！！)。

谢谢你的帮助。

Answer 1

是的，因为端口443通常用于HTTPS，所以您必须使用ALPN来指示您正在使用'x-amzn- MQTT -ca‘协议名在端口443上使用TLS与mqtt通信。

此blog post给出了为Paho-MQTT客户端设置ALPN的示例。

您可能需要仔细检查的另一件事是

您在客户端上使用的客户端证书已在IoT

1. 中注册，您已注册的证书附带了允许执行MQTT connection/publish/subscribe/receive.

等操作的a policy

如果证书或策略不正确，则可能会完成TLS握手，但亚马逊网络服务IoT将很快结束连接。

Answer 2

我没有发现或解决这个代码的问题，而是使用了AWS SDK for C，现在一切正常。