Dart mqtt_client identifierRejected and a disconnection origin of none

Question

Flutter information:

Flutter 1.22.6 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 9b2d32b605 (3 weeks ago) • 2021-01-22 14:36:39 -0800
Engine • revision 2f0af37152
Tools • Dart 2.10.5

I'm trying to use mqtt_client to connect to a broker (emqx) though I've also trying hivemq and get the same error. The code I'm using to connect is:

import 'package:mqtt_client/mqtt_client.dart';
import 'package:mqtt_client/mqtt_server_client.dart';

class MqttTest {

  Future<MqttServerClient> connect() async {
    MqttServerClient client = MqttServerClient.withPort('<ip redacted>', 'client-1', 1883);
    client.logging(on: true);
    client.onConnected = onConnected;
    client.onDisconnected = onDisconnected;
    client.onUnsubscribed = onUnsubscribed;
    client.onSubscribed = onSubscribed;
    client.onSubscribeFail = onSubscribeFail;
    client.pongCallback = pong;

    final connMessage = MqttConnectMessage()
      .keepAliveFor(60)
      .withWillTopic('willtopic')
      .withWillMessage('willMessage')
      .startClean()
      .withWillQos(MqttQos.atLeastOnce);

    client.connectionMessage = connMessage;

    try {
      await client.connect();
    } catch(e) {
      print('Exception: $e');
      client.disconnect();
    }

    client.updates.listen((List<MqttReceivedMessage<MqttMessage>> c) {
      final MqttPublishMessage message = c[0].payload;
      final payload = MqttPublishPayload.bytesToStringAsString(message.payload.message);

      print('Received message:$payload from topic: ${c[0].topic}>');
    });

    return client;
  }

  void onConnected() {
    print('Connected');
  }

  void onDisconnected() {
    print('Disconnected');
  }

  void onSubscribed(String topic) {
    print('Subscribed topic: $topic');
  }

  void onSubscribeFail(String topic) {
    print('Failed to subscribe $topic');
  }

  void onUnsubscribed(String topic) {
    print('Unsubscribed topic: $topic');
  }

  void pong() {
    print('Ping response client callback invoked');
  }
}

Here are the logs when trying to connect:

I/flutter ( 9784): 2-2021-02-12 20:25:05.602730 -- MqttConnectionHandlerBase::connect - server 192.168.0.34, port 1883
I/flutter ( 9784): 2-2021-02-12 20:25:05.603044 -- SynchronousMqttServerConnectionHandler::internalConnect entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.603131 -- SynchronousMqttServerConnectionHandler::internalConnect - initiating connection try 0, auto reconnect in progress false
I/flutter ( 9784): 2-2021-02-12 20:25:05.603230 -- SynchronousMqttServerConnectionHandler::internalConnect - insecure TCP selected
I/flutter ( 9784): 2-2021-02-12 20:25:05.603668 -- SynchronousMqttServerConnectionHandler::internalConnect - calling connect
I/flutter ( 9784): 2-2021-02-12 20:25:05.603767 -- MqttNormalConnection::connect - entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.662356 -- MqttServerConnection::_startListening
I/flutter ( 9784): 2-2021-02-12 20:25:05.662832 -- SynchronousMqttServerConnectionHandler::internalConnect - connection complete
I/flutter ( 9784): 2-2021-02-12 20:25:05.663126 -- SynchronousMqttServerConnectionHandler::internalConnect sending connect message
I/flutter ( 9784): 2-2021-02-12 20:25:05.663404 -- MqttConnectionHandlerBase::sendMessage - MQTTMessage of type MqttMessageType.connect
I/flutter ( 9784): Header: MessageType = MqttMessageType.connect, Duplicate = false, Retain = false, Qos = MqttQos.atMostOnce, Size = 0
I/flutter ( 9784): Connect Variable Header: ProtocolName=MQIsdp, ProtocolVersion=3, ConnectFlags=Connect Flags: Reserved1=false, CleanStart=true, WillFlag=true, WillQos=MqttQos.atLeastOnce, WillRetain=false, PasswordFlag=false, UserNameFlag=false, KeepAlive=60
I/flutter ( 9784): MqttConnectPayload - client identifier is : 
I/flutter ( 9784): 2-2021-02-12 20:25:05.666395 -- SynchronousMqttServerConnectionHandler::internalConnect - pre sleep, state = Connection status is connecting with return code of noneSpecified and a disconnection origin of none
I/flutter ( 9784): 2-2021-02-12 20:25:05.670081 -- MqttConnection::_onData
I/flutter ( 9784): 2-2021-02-12 20:25:05.670414 -- MqttServerConnection::_onData - message received MQTTMessage of type MqttMessageType.connectAck
I/flutter ( 9784): Header: MessageType = MqttMessageType.connectAck, Duplicate = false, Retain = false, Qos = MqttQos.atMostOnce, Size = 2
I/flutter ( 9784): Connect Variable Header: TopicNameCompressionResponse={0}, ReturnCode={MqttConnectReturnCode.identifierRejected}
I/flutter ( 9784): 2-2021-02-12 20:25:05.670585 -- MqttServerConnection::_onData - message available event fired
I/flutter ( 9784): 2-2021-02-12 20:25:05.671317 -- MqttConnectionHandlerBase::_connectAckProcessor
I/flutter ( 9784): 2-2021-02-12 20:25:05.671420 -- MqttConnectionHandlerBase::_connectAckProcessor connection rejected
I/flutter ( 9784): 2-2021-02-12 20:25:05.671510 -- MqttConnectionHandlerBase::_performConnectionDisconnect entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.671632 -- MqttConnectionHandlerBase:: cancelling connect timer
I/flutter ( 9784): 2-2021-02-12 20:25:05.672389 -- MqttConnectionBase::_onDone - calling disconnected callback
I/flutter ( 9784): 2-2021-02-12 20:25:05.672538 -- SynchronousMqttServerConnectionHandler::internalConnect - post sleep, state = Connection status is disconnected with return code of identifierRejected and a disconnection origin of none
I/flutter ( 9784): 2-2021-02-12 20:25:05.672625 -- SynchronousMqttServerConnectionHandler::internalConnect - initiating connection try 1, auto reconnect in progress false
I/flutter ( 9784): 2-2021-02-12 20:25:05.672687 -- SynchronousMqttServerConnectionHandler::internalConnect - insecure TCP selected
I/flutter ( 9784): 2-2021-02-12 20:25:05.672755 -- SynchronousMqttServerConnectionHandler::internalConnect - calling connect
I/flutter ( 9784): 2-2021-02-12 20:25:05.672805 -- MqttNormalConnection::connect - entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.689565 -- MqttServerConnection::_startListening
I/flutter ( 9784): 2-2021-02-12 20:25:05.690119 -- SynchronousMqttServerConnectionHandler::internalConnect - connection complete
I/flutter ( 9784): 2-2021-02-12 20:25:05.690352 -- SynchronousMqttServerConnectionHandler::internalConnect sending connect message
I/flutter ( 9784): 2-2021-02-12 20:25:05.690550 -- MqttConnectionHandlerBase::sendMessage - MQTTMessage of type MqttMessageType.connect
I/flutter ( 9784): Header: MessageType = MqttMessageType.connect, Duplicate = false, Retain = false, Qos = MqttQos.atMostOnce, Size = 38
I/flutter ( 9784): Connect Variable Header: ProtocolName=MQIsdp, ProtocolVersion=3, ConnectFlags=Connect Flags: Reserved1=false, CleanStart=true, WillFlag=true, WillQos=MqttQos.atLeastOnce, WillRetain=false, PasswordFlag=false, UserNameFlag=false, KeepAlive=60
I/flutter ( 9784): MqttConnectPayload - client identifier is : 
I/flutter ( 9784): 2-2021-02-12 20:25:05.692258 -- SynchronousMqttServerConnectionHandler::internalConnect - pre sleep, state = Connection status is connecting with return code of noneSpecified and a disconnection origin of none
I/flutter ( 9784): 2-2021-02-12 20:25:05.695322 -- MqttConnection::_onData
I/flutter ( 9784): 2-2021-02-12 20:25:05.695474 -- MqttServerConnection::_onData - message received MQTTMessage of type MqttMessageType.connectAck
I/flutter ( 9784): Header: MessageType = MqttMessageType.connectAck, Duplicate = false, Retain = false, Qos = MqttQos.atMostOnce, Size = 2
I/flutter ( 9784): Connect Variable Header: TopicNameCompressionResponse={0}, ReturnCode={MqttConnectReturnCode.identifierRejected}
I/flutter ( 9784): 2-2021-02-12 20:25:05.695566 -- MqttServerConnection::_onData - message available event fired
I/flutter ( 9784): 2-2021-02-12 20:25:05.695650 -- MqttConnectionHandlerBase::_connectAckProcessor
I/flutter ( 9784): 2-2021-02-12 20:25:05.695708 -- MqttConnectionHandlerBase::_connectAckProcessor connection rejected
I/flutter ( 9784): 2-2021-02-12 20:25:05.695777 -- MqttConnectionHandlerBase::_performConnectionDisconnect entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.695836 -- MqttConnectionHandlerBase:: cancelling connect timer
I/flutter ( 9784): 2-2021-02-12 20:25:05.696047 -- MqttConnectionBase::_onDone - calling disconnected callback
I/flutter ( 9784): 2-2021-02-12 20:25:05.696120 -- SynchronousMqttServerConnectionHandler::internalConnect - post sleep, state = Connection status is disconnected with return code of identifierRejected and a disconnection origin of none
I/flutter ( 9784): 2-2021-02-12 20:25:05.696170 -- SynchronousMqttServerConnectionHandler::internalConnect - initiating connection try 2, auto reconnect in progress false
I/flutter ( 9784): 2-2021-02-12 20:25:05.696574 -- SynchronousMqttServerConnectionHandler::internalConnect - insecure TCP selected
I/flutter ( 9784): 2-2021-02-12 20:25:05.696646 -- SynchronousMqttServerConnectionHandler::internalConnect - calling connect
I/flutter ( 9784): 2-2021-02-12 20:25:05.696697 -- MqttNormalConnection::connect - entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.708657 -- MqttServerConnection::_startListening
I/flutter ( 9784): 2-2021-02-12 20:25:05.708823 -- SynchronousMqttServerConnectionHandler::internalConnect - connection complete
I/flutter ( 9784): 2-2021-02-12 20:25:05.708878 -- SynchronousMqttServerConnectionHandler::internalConnect sending connect message
I/flutter ( 9784): 2-2021-02-12 20:25:05.708960 -- MqttConnectionHandlerBase::sendMessage - MQTTMessage of type MqttMessageType.connect
I/flutter ( 9784): Header: MessageType = MqttMessageType.connect, Duplicate = false, Retain = false, Qos = MqttQos.atMostOnce, Size = 38
I/flutter ( 9784): Connect Variable Header: ProtocolName=MQIsdp, ProtocolVersion=3, ConnectFlags=Connect Flags: Reserved1=false, CleanStart=true, WillFlag=true, WillQos=MqttQos.atLeastOnce, WillRetain=false, PasswordFlag=false, UserNameFlag=false, KeepAlive=60
I/flutter ( 9784): MqttConnectPayload - client identifier is : 
I/flutter ( 9784): 2-2021-02-12 20:25:05.709719 -- SynchronousMqttServerConnectionHandler::internalConnect - pre sleep, state = Connection status is connecting with return code of noneSpecified and a disconnection origin of none
I/flutter ( 9784): 2-2021-02-12 20:25:05.713511 -- MqttConnection::_onData
I/flutter ( 9784): 2-2021-02-12 20:25:05.713653 -- MqttServerConnection::_onData - message received MQTTMessage of type MqttMessageType.connectAck
I/flutter ( 9784): Header: MessageType = MqttMessageType.connectAck, Duplicate = false, Retain = false, Qos = MqttQos.atMostOnce, Size = 2
I/flutter ( 9784): Connect Variable Header: TopicNameCompressionResponse={0}, ReturnCode={MqttConnectReturnCode.identifierRejected}
I/flutter ( 9784): 2-2021-02-12 20:25:05.713730 -- MqttServerConnection::_onData - message available event fired
I/flutter ( 9784): 2-2021-02-12 20:25:05.713811 -- MqttConnectionHandlerBase::_connectAckProcessor
I/flutter ( 9784): 2-2021-02-12 20:25:05.713867 -- MqttConnectionHandlerBase::_connectAckProcessor connection rejected
I/flutter ( 9784): 2-2021-02-12 20:25:05.713920 -- MqttConnectionHandlerBase::_performConnectionDisconnect entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.713973 -- MqttConnectionHandlerBase:: cancelling connect timer
I/flutter ( 9784): 2-2021-02-12 20:25:05.716320 -- MqttConnectionBase::_onDone - calling disconnected callback
I/flutter ( 9784): 2-2021-02-12 20:25:05.716455 -- SynchronousMqttServerConnectionHandler::internalConnect - post sleep, state = Connection status is disconnected with return code of identifierRejected and a disconnection origin of none
I/flutter ( 9784): 2-2021-02-12 20:25:05.716550 -- SynchronousMqttServerConnectionHandler::internalConnect failed
I/flutter ( 9784): Exception: mqtt-client::NoConnectionException: The maximum allowed connection attempts ({3}) were exceeded. The broker is not responding to the connection request message correctly The return code is MqttConnectReturnCode.identifierRejected
I/flutter ( 9784): 2-2021-02-12 20:25:05.716842 -- MqttConnectionHandlerBase::disconnect - entered
I/flutter ( 9784): 2-2021-02-12 20:25:05.716915 -- MqttConnectionHandlerBase::_performConnectionDisconnect entered
I/flutter ( 9784): Disconnected

Answer 1

Before you call await client.connect() add this line:

client.keepAlivePeriod = 20;

This line is NOT mandatory when you use the client id in MqttServerClient('homeassistant', 'touchsr'):

.withClientIdentifier('Mqtt_MyClientUniqueId')

Answer 2

I was facing the same issue And resolved it. Before I was using Hivemqtt in my flutter app and faced the same issue so later on I use MQTTx.

Below I have mentioned the steps to resolve the issue.

1. Use the latest MQTT flutter dependency
2. Download MQTTX.Setup.1.7.2.exe , Link
3. Open the MQTTX.exe then connect to the server by giving any random name
4. Use MqttServerClient.withPort('broker.emqx.io', 'flutter_client', 1883); and rest of the code will be same
5. Then run your app. It will work

N:P: Make sure to restart the MQTT server before connecting with the mobile device

Answer 3

As it turns out the issue was that if you create MqttConnectMessage then the client id in the constructor is ignored. I had to add withClientIdentifier("client-1") to my MqttConnectMessage.