Eclipse paho Mqtt:Getting java.io.EOF Exception

问题

I am getting "java.io.eof" exception,when i am trying to subscribe mqtt client. I am using eclipse paho library and using mosquitto broker. I am not getting any answer of this,so please help me why this happens ?

Mqtt connection and subscribe

I am using this code for connecting and subscribing to mosquitto

private void buildClient(String clientId){
    log.debug("Connecting... "+clientId);
        try {
            mqttClient = new MqttClient(envConfiguration.getBrokerUrl(), clientId,new MemoryPersistence());
            System.out.println(mqttClient.isConnected());
        } catch (MqttException e) {
            log.debug("build client stopped due to "+e.getCause());
        }

        chatCallback = new ChatCallback(this.userService,this);
        mqttClient.setCallback(chatCallback);
        mqttConnectOptions = new MqttConnectOptions();
        mqttConnectOptions.setCleanSession(true);
    }

    @Override
    public void connect(String clientId,String topic) {

        try{
            if(mqttClient == null || !mqttClient.getClientId().equals(clientId)){
                buildClient(clientId);
                mqttClient.connect(mqttConnectOptions);
                subscribe(clientId,topic);
            } 
        }catch (Exception e) {
            log.debug("connection attempt failed "+ e.getCause() + " trying...");
        }
    }

    @Override
    public void subscribe(String clientId,String topic) throws MqttException {
        if(mqttClient != null && mqttClient.isConnected()){

            mqttClient.subscribe(topic,0);
            /*try {
                log.debug("Subscribing... with client id :: " + clientId + "topic");
                mqttClient.subscribe(topic,2);
            } catch (MqttException e) {
                log.debug("subscribing error.."+e.getLocalizedMessage());
            }*/
        }

    }
}

And mqtt call back

@Override
public void connectionLost(Throwable arg0) {
    log.debug("Connection lost... attampting retrying due to "
                    + arg0);
    arg0.printStackTrace();
    // chatServiceimpl.connect();

}

@Override
public void deliveryComplete(IMqttDeliveryToken arg0) {
    log.debug("delivered message" + arg0);
    // TODO Auto-generated method stub

}

@Override
public void messageArrived(String arg0, MqttMessage arg1) throws Exception {

    log.debug("Message recived..." + arg1.toString());
    userService.saveChat(arg1.toString());
 }

I am facing this error when i am subscribing to mosquitto

Error logs

2015-11-30/18:19:00.877 [MQTT Call: 25287] DEBUG c.s.s.ChatCallback: Message recived...{ "id":"37153topic25287T1448886285.79573", "from":"37153", "to":"25287", "chatBody":[{"type": "text", "message":"The fact "}]}
2015-11-30/18:19:00.878 [MQTT Call: 25287] DEBUG c.s.s.u.UserService: Saving chat...
2015-11-30/18:19:00.883 [MQTT Call: 25287] DEBUG c.s.s.u.UserService: Get user by id::37153
2015-11-30/18:19:00.885 [MQTT Call: 25287] DEBUG c.s.s.u.UserService: Get user by id::25287
2015-11-30/18:19:00.886 [MQTT Rec: 25287] DEBUG c.s.s.ChatCallback: Connection lost... attampting retrying due to Connection lost (32109) - java.io.EOFException
Connection lost (32109) - java.io.EOFException
    at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:138)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.EOFException
    at java.io.DataInputStream.readByte(DataInputStream.java:267)
    at org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(MqttInputStream.java:56)
    at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:100)
    ... 1 more

Mosquitto Logs

1448889230: Client 25287 disconnected.
1448889230: New client connected from 192.168.2.63 as 25287 (c0, k60).
1448889231: New connection from 192.168.2.242 on port 1883.
1448889231: Client 25287 already connected, closing old connection.
1448889231: Client 25287 disconnected.
1448889231: New client connected from 192.168.2.242 as 25287 (c1, k60).
1448889231: New connection from 192.168.2.63 on port 1883.
1448889231: Client 25287 already connected, closing old connection.
1448889231: Client 25287 disconnected.
1448889231: New client connected from 192.168.2.63 as 25287 (c0, k60).
1448889269: New connection from 192.168.2.242 on port 1883.

回答1:

You have multiple clients connecting to the broker with the same clientid, this is not allowed and as one connects the broker will disconnect the currently connected client.

If both clients have automatic reconnection logic then they will just continue to kick each other off.

Change the client id on one of the clients.

回答2:

As hardillb mentioned above, you have multiple clients connecting. Server (mosquitto) will disconnect the old connection when it receives a connect request from the same client again.

use the isConnected() method on MqttClient object to know if its connected. for eg.

if (! m_client.isConnected()) {
  // reconnect
}

来源：https://stackoverflow.com/questions/33998919/eclipse-paho-mqttgetting-java-io-eof-exception

标签

java

mqtt

paho