title: Mqtt broker， closing old connection
body: <p>mqtt client has same client id。
  how  to closing old connection?
  just like this.</p>
  
  <pre><code>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').
  </code></pre>
  
  <p>EDIT:</p>
  
  <pre><code> 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();
      }
  }
  </code></pre>
  
  <p>if the clientid is same,has error.</p>
  
  <p>ConnectionLost,cause:(32109) - java.io.EOFException</p>