MQTT connection disconnected after connected successfully

Vijay R. Gawade

Hi All

I am using Qt 5.9 with QMQTT-Emqx MQTT library for MQTT communication.

Currently, we have locally installed a mosquitto broker and configured it to use an SSL certificate with the client certificate required on Port 8883.

In our app, we connected to the broker with CA & Client certificate with the following code

    QSslConfiguration sslConfig;
    sslConfig.defaultConfiguration();
    sslConfig.setProtocol(QSsl::TlsV1_2);
    sslConfig.setPeerVerifyMode(QSslSocket::AutoVerifyPeer);
    sslConfig.setCaCertificates(caCertsList);
    sslConfig.setLocalCertificate(certs.first());
    sslConfig.setPrivateKey(QSslKey(clientKeyFile.readAll(), QSsl::Rsa));

    m_client = new QMQTT::Client("192.168.1.13", 8883, sslConfig, true);
    m_client->setClientId(MQTTConstant::clientId);

    connect(m_client, &QMQTT::Client::connected, this, &MqttController::onConnected);
    connect(m_client, &QMQTT::Client::disconnected, this, &MqttController::onDisconnected);
    connect(m_client, &QMQTT::Client::error, this, &MqttController::onError);

    m_client->setKeepAlive(10);
    m_client->setAutoReconnectInterval(1000);
    m_client->setCleanSession(true);
    m_client->setAutoReconnect(true);
    m_client->connectToHost();

Also I checked SSL library details as follows:

SSL Library Build Version: "OpenSSL 1.0.2j 26 Sep 2016"
SSL Support: true
SSL Library Version: "OpenSSL 1.0.2e 3 Dec 2015"

In onConnected() function I also able to publish messages successfully
But after that following logs are appearing

2022-06-30T16:24:00.639+05:30 ~ INF ~ controller.mqtt      ~ Disconnected from MQTT Broker !!!     isConnectedToHost false
2022-06-30T16:24:00.643+05:30 ~ INF ~ controller.mqtt      ~ MqttController: Connected to MQTT Broker !!!
2022-06-30T16:24:00.646+05:30 ~ INF ~ controller.mqtt      ~ Subscribing to sensor/rtdata topic:  true
2022-06-30T16:24:00.652+05:30 ~ WRN ~ controller.mqtt      ~ Device is listening messages for Topic:  "sensor/rtdata"
2022-06-30T16:24:00.654+05:30 ~ WRN ~ controller.mqtt      ~ New Message Arrived... Topic: "sensor/rtdata"    Payload: "This is test msg from windows-laptop"
2022-06-30T16:24:00.657+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost true
2022-06-30T16:24:00.661+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost true
2022-06-30T16:24:00.664+05:30 ~ INF ~ controller.mqtt      ~ Disconnected from MQTT Broker !!!     isConnectedToHost false
2022-06-30T16:24:00.667+05:30 ~ INF ~ controller.mqtt      ~ MqttController: Connected to MQTT Broker !!!
2022-06-30T16:24:00.669+05:30 ~ WRN ~ controller.mqtt      ~ Device is not connected to MQTT Broker !!!
2022-06-30T16:24:00.671+05:30 ~ INF ~ controller.mqtt      ~ Subscribing to sensor/rtdata topic:  false
2022-06-30T16:24:00.744+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost false
2022-06-30T16:24:00.747+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost false
2022-06-30T16:24:00.750+05:30 ~ INF ~ controller.mqtt      ~ Disconnected from MQTT Broker !!!     isConnectedToHost false
2022-06-30T16:24:00.752+05:30 ~ INF ~ controller.mqtt      ~ MqttController: Connected to MQTT Broker !!!
2022-06-30T16:24:00.754+05:30 ~ WRN ~ controller.mqtt      ~ Device is not connected to MQTT Broker !!!
2022-06-30T16:24:00.756+05:30 ~ INF ~ controller.mqtt      ~ Subscribing to sensor/rtdata topic:  false
2022-06-30T16:24:00.788+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost false
2022-06-30T16:24:00.791+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost false
2022-06-30T16:24:00.794+05:30 ~ INF ~ controller.mqtt      ~ Disconnected from MQTT Broker !!!     isConnectedToHost false
2022-06-30T16:24:00.798+05:30 ~ INF ~ controller.mqtt      ~ MqttController: Connected to MQTT Broker !!!
2022-06-30T16:24:00.800+05:30 ~ WRN ~ controller.mqtt      ~ Device is not connected to MQTT Broker !!!
2022-06-30T16:24:00.802+05:30 ~ INF ~ controller.mqtt      ~ Subscribing to sensor/rtdata topic:  false
2022-06-30T16:24:00.907+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost false
2022-06-30T16:24:00.910+05:30 ~ DBG ~ controller.mqtt      ~ MQTT SSL Error:  QMQTT::ClientError(SocketRemoteHostClosedError)    isConnectedToHost false
2022-06-30T16:24:00.913+05:30 ~ INF ~ controller.mqtt      ~ Disconnected from MQTT Broker !!!     isConnectedToHost false

mosquitto configs:

# secure port with client certificate required
listener 8883
allow_anonymous false
cafile C:\Program Files\mosquitto\certs\ca.crt
certfile C:\Program Files\mosquitto\certs\broker.crt
keyfile C:\Program Files\mosquitto\certs\broker.key
require_certificate true
use_identity_as_username true
tls_version tlsv1.2

And above works as expected with mosquitto_sub/mosquitto_pub and another 3rd party MQTT X client tool without any issue

$ mosquitto_pub -h 192.168.1.13 -p 8883 --cafile ca.crt --cert client.crt --key client.key -t test -m "This is message sent over secure port 8883 with client cert with CN as username"

SGaist

Hi,

You should check that with the library author.

Did you consider using the official QtMqtt module ?

Vijay R. Gawade

@SGaist Is the official QtMqtt module available for Qt 5.9? when I tried to import it for Qt 5.9, I was getting an unknown module error as follows:
pro file:

QT += mqtt
QT += qmqtt

While building getting following error:

:-1: error: Unknown module(s) in QT: mqtt
:-1: error: Project ERROR: Unknown module(s) in QT: qmqtt

According to the qtmqtt repo, the minimum supported version is 5.10. That's why I am using the Emqx's qmqtt library.

in which one open issue is there which look related to this:
https://github.com/emqx/qmqtt/issues/187

In which they are mentioning some bug related to QTcpSocket, When the remote peer uses shutdown any operation on its end, the local QTcpSocket closes the connection (RemoteHostClosedError).
https://bugreports.qt.io/browse/QTBUG-39518

@SGaist Can you please suggest to me which library or module I can use for MQTT with Qt 5.9?

ChrisW67

@Vijay-R-Gawade Did you actually try it, or just assume that because there was no branch 5.9 that it was not possible?

Others have had success: https://forum.qt.io/topic/101940/what-s-the-minimum-version-for-qtmqtt

Is there a reason for developing a new project on an old version of Qt 5?

Vijay R. Gawade

@ChrisW67 yes, I have not tried to build it for Qt 5.8
I will try to build & use this official module.

And regarding the older qt version, yes we have device dependency, BSP not yet supported[in development]