Question

mqtt客户端具有相同的客户端ID。如何关闭旧连接？就像这样。

New connection from 192.168.3.57 on port 1883.
1479826181: Client paho166768969170988 already connected, closing old connection.
1479826181: Client paho166768969170988 disconnected.
1479826181: New client connected from 192.168.3.57 as paho166768969170988 (c1, k60, u'admin').

编辑：

 String clientId ="**public_cloud**";
    try {
        MqttClient sampleClient = new MqttClient(config.getBroker(), clientId);
        sampleClient.setCallback(new PushCallback());

        MqttTopic mtopic = sampleClient.getTopic(config.getTopic());

        MqttConnectOptions connOpts = new MqttConnectOptions();
        connOpts.setCleanSession(true);
        connOpts.setConnectionTimeout(100);
        connOpts.setKeepAliveInterval(200);
        connOpts.setUserName(config.getUsername());
        connOpts.setPassword(config.getPassword().toCharArray());
        connOpts.setWill(mtopic, "close".getBytes(), 0, true);

        sampleClient.connect(connOpts);
    } catch (MqttException e) {
        e.printStackTrace();
    }
}

如果clientid相同，则有错误。

ConnectionLost，cause：（32109） - java.io.EOFException

Answer 1

 String clientId ="**public_cloud**";
    try {
        MqttClient sampleClient = new MqttClient(config.getBroker(), clientId);
        sampleClient.setCallback(new PushCallback());

        MqttTopic mtopic = sampleClient.getTopic(config.getTopic());

        MqttConnectOptions connOpts = new MqttConnectOptions();
        connOpts.setCleanSession(true);
        connOpts.setConnectionTimeout(100);
        connOpts.setKeepAliveInterval(200);
        connOpts.setUserName(config.getUsername());
        connOpts.setPassword(config.getPassword().toCharArray());
        connOpts.setWill(mtopic, "close".getBytes(), 0, true);

        sampleClient.connect(connOpts);
    } catch (MqttException e) {
        e.printStackTrace();
    }
}

如果clientId相同，则会出现错误：

ConnectionLost，cause：（32109） - java.io.EOFException

Answer 2

与代理的每个连接必须具有唯一的客户端ID。这是MQTT规范的一部分。代理如何使用现有客户端ID处理新连接，但大多数将断开最旧的连接。

您所看到的情况中的常见修复是使用随机生成的客户端ID或当前时间戳

long time = new Date().getTime();
String clientId ="public_cloud" + time;
    try {
        MqttClient sampleClient = new MqttClient(config.getBroker(), clientId);
        sampleClient.setCallback(new PushCallback());

        MqttTopic mtopic = sampleClient.getTopic(config.getTopic());

        MqttConnectOptions connOpts = new MqttConnectOptions();
        connOpts.setCleanSession(true);
        connOpts.setConnectionTimeout(100);
        connOpts.setKeepAliveInterval(200);
        connOpts.setUserName(config.getUsername());
        connOpts.setPassword(config.getPassword().toCharArray());
        connOpts.setWill(mtopic, "close".getBytes(), 0, true);

        sampleClient.connect(connOpts);
    } catch (MqttException e) {
        e.printStackTrace();
    }
}

Mqtt经纪人，关闭旧连接

2 个答案: