Question

如何实现ping请求？我按照这个代码。我阅读了以下链接How to send ping using Eclipse Paho MQTT client?。但是我无法实现它。

package mqttTestJava;

    import org.eclipse.paho.client.mqttv3.MqttClient;
    import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
    import org.eclipse.paho.client.mqttv3.MqttException;
    import org.eclipse.paho.client.mqttv3.MqttMessage;
    import org.eclipse.paho.client.mqttv3.MqttPingSender;
    import org.eclipse.paho.client.mqttv3.internal.ClientComms;
    import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
    import org.eclipse.paho.client.mqttv3.MqttCallback;
    import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;


    class SimpleCallback implements MqttCallback, MqttPingSender  {
        private String instanceData = "";
            @Override
            public void connectionLost(Throwable cause) { //Called when the client lost the connection to the broker

                System.out.println("Connection lost on instance \"" + instanceData + "\" with cause \"" + cause.getMessage() + "\" Reason code " +
                        ((MqttException)cause).getReasonCode() + "\" Cause \"" +
                        ((MqttException)cause).getCause() + "\"");
                        cause.printStackTrace();
            }

            @Override
            public void messageArrived(String topic, MqttMessage message) throws Exception {
                System.out.println("-------------------------------------------------");
                System.out.println("| Topic:" + topic);
                System.out.println("message arived "+new String(message.getPayload()));
                System.out.println("-------------------------------------------------");

            }

            @Override
            public void deliveryComplete(IMqttDeliveryToken token) {//Called when a outgoing publish is complete
            }

            //for ping request 

            @Override
            public void init(ClientComms arg0) {
                // TODO Auto-generated method stub

            }

            @Override
            public void schedule(long arg0) {
                // TODO Auto-generated method stub

            }

            @Override
            public void start() {
                // TODO Auto-generated method stub

            }

            @Override
            public void stop() {
                // TODO Auto-generated method stub

            }
    }


    public class mqttTest {
        public static void main(String[] args){
            String topic = "56";
            String content = "Message form java";
            int qos = 2;
            String broker = "tcp://iot.eclipse.org:1883";
            String clientId = "234";
            MemoryPersistence persistence = new MemoryPersistence();

            try {

                MqttClient sampleClient = new MqttClient(broker, clientId,persistence);

                MqttConnectOptions connOpts = new MqttConnectOptions();
                connOpts.setCleanSession(false);
               // connOpts.setKeepAliveInterval(3000);

                System.out.println("Connecting to broker: " + broker);
                sampleClient.connect(connOpts);

                sampleClient.subscribe(topic, 2);
                System.out.println("Connected");
                System.out.println("Publish message: " + content);
                MqttMessage message = new MqttMessage(content.getBytes());
                message.setQos(qos);
                sampleClient.setCallback(new SimpleCallback());
                sampleClient.publish(topic, message);
                System.out.println("Message published");
                try {
                 // Thread.sleep(5000);
                  //  sampleClient.disconnect();
                } catch(Exception e) {
                    e.printStackTrace();
                }
               // System.out.println("Disconnected");
               // System.exit(0);
            } catch(MqttException me){
                System.out.println("reason " + me.getReasonCode());
                System.out.println("msg " + me.getMessage());
                System.out.println("loc " + me.getLocalizedMessage());
                System.out.println("cause " + me.getCause());
                System.out.println("except " + me);
                me.printStackTrace();
            }
        }
    }

发生错误后几分钟：

Connection lost on instance "" with cause "Connection lost" Reason code 32109" Cause "java.net.SocketException: Connection reset"
Connection lost (32109) - java.net.SocketException: Connection reset
    at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:146)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.SocketException: Connection reset
    at java.net.SocketInputStream.read(SocketInputStream.java:196)
    at java.net.SocketInputStream.read(SocketInputStream.java:122)
    at java.net.SocketInputStream.read(SocketInputStream.java:210)
    at java.io.DataInputStream.readByte(DataInputStream.java:265)
    at org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(MqttInputStream.java:65)
    at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:107)
    ... 1 more

Answer 1

如果您使用标准＆amp;最新的Paho客户端，您不必实现ping请求模块。 Paho具有内置功能。您必须在建立连接时设置Keepalive间隔，并且Paho在后端处理PINGREQ和PINGRESP。

问题可能出在代理设置中，或尝试使用不同的keepalive值。

如何在mqtt客户端中实现ping请求

1 个答案: