MqttException（0） - AndroidThings上的java.net.NoRouteToHostException

Question

我正在試用Android預覽模式下的東西。
面對通過代碼與WiFi以及本地網絡通信面臨的很多挑戰。
其中一種情況是在RPi3上將Android Thing作爲MQTT代理。
我不確定問題是否與MQTT代碼或Android事物有關。

任何人都可以幫助我找出問題嗎？
這裏是我的代碼：

package com.example.androidthings.myproject; 

import android.app.Activity; 
import android.os.Bundle; 
import android.util.Log; 

import com.google.android.things.pio.Gpio; 
import com.google.android.things.pio.PeripheralManagerService; 

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken; 
import org.eclipse.paho.client.mqttv3.MqttCallback; 
import org.eclipse.paho.client.mqttv3.MqttClient; 
import org.eclipse.paho.client.mqttv3.MqttException; 
import org.eclipse.paho.client.mqttv3.MqttMessage; 
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence; 

import java.io.IOException; 

    public class MainActivity extends Activity implements MqttCallback{ 
    private static final String TAG = MainActivity.class.getSimpleName(); 

    public static final String MOTOR_A_PIN_1 = "BCM21"; //physical pin #40 
    public static final String MOTOR_A_PIN_2 = "BCM20"; //physical pin #38 
    public static final String MOTOR_B_PIN_1 = "BCM24"; //physical pin #18 
    public static final String MOTOR_B_PIN_2 = "BCM23"; //physical pin #16 

    private Gpio motorAPin1; 
    private Gpio motorAPin2; 
    private Gpio motorBPin1; 
    private Gpio motorBPin2; 

    private MqttClient client; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     Log.d(TAG, "onCreate.....Motor MQTT"); 

     try { 
      MemoryPersistence persistance = new MemoryPersistence(); 
      client = new MqttClient("tcp://127.0.0.1:1883", "AndroidThingBroker", persistance); 
      client.connect(); 

      String topic = "topic/androidthings"; 
      int qos = 1; 
      client.subscribe(topic, qos); 

     } catch (MqttException e) { 
      e.printStackTrace(); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

     PeripheralManagerService service = new PeripheralManagerService(); 
     try { 

      // Create GPIO connection for L293D (Motor will run through L293D). 
      motorAPin1 = service.openGpio(MOTOR_A_PIN_1); 
      // Configure as an output. 
      motorAPin1.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW); 

      // Create GPIO connection for L293D (Motor will run through L293D). 
      motorAPin2 = service.openGpio(MOTOR_A_PIN_2); 
      // Configure as an output. 
      motorAPin2.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW); 

      // Create GPIO connection for L293D (Motor will run through L293D). 
      motorBPin1 = service.openGpio(MOTOR_B_PIN_1); 
      // Configure as an output. 
      motorBPin1.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW); 

      // Create GPIO connection for L293D (Motor will run through L293D). 
      motorBPin2 = service.openGpio(MOTOR_B_PIN_2); 
      // Configure as an output. 
      motorBPin2.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW); 

     } catch (IOException e) { 
      Log.e(TAG, "Error on PeripheralIO API", e); 
     } 


    } 

    @Override 
    protected void onDestroy() { 
     super.onDestroy(); 
     Log.d(TAG, "onDestroy"); 

     if (motorAPin1 != null) { 
      try { 
       motorAPin1.close(); 
      } catch (IOException e) { 
       Log.e(TAG, "Error on PeripheralIO API", e); 
      } 
     } 

     if (motorAPin2 != null) { 
      try { 
       motorAPin2.close(); 
      } catch (IOException e) { 
       Log.e(TAG, "Error on PeripheralIO API", e); 
      } 
     } 

     if (motorBPin1 != null) { 
      try { 
       motorBPin1.close(); 
      } catch (IOException e) { 
       Log.e(TAG, "Error on PeripheralIO API", e); 
      } 
     } 

     if (motorBPin2 != null) { 
      try { 
       motorBPin2.close(); 
      } catch (IOException e) { 
       Log.e(TAG, "Error on PeripheralIO API", e); 
      } 
     } 
    } 

    @Override 
    public void connectionLost(Throwable cause) { 
     Log.d(TAG, "connectionLost...."); 
    } 

    @Override 
    public void messageArrived(String topic, MqttMessage message) throws Exception { 
     String payload = new String(message.getPayload()); 
     Log.d(TAG, payload); 
     // do stuff 
    } 

    @Override 
    public void deliveryComplete(IMqttDeliveryToken token) { 
     Log.d(TAG, "deliveryComplete...."); 
    } 
} 

錯誤：

12-27 15:03:58.898 2245-2245/com.example.androidthings.myproject W/System.err: 
Unable to connect to server (32103) - java.net.ConnectException: Connection refused 
12-27 15:03:58.898 2245-2245/com.example.androidthings.myproject W/System.err:  at org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:79) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:590) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.lang.Thread.run(Thread.java:761) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err: Caused by: java.net.ConnectException: Connection refused 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.net.PlainSocketImpl.socketConnect(Native Method) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:334) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:196) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:356) 
12-27 15:03:58.899 2245-2245/com.example.androidthings.myproject W/System.err:  at java.net.Socket.connect(Socket.java:586) 
12-27 15:03:58.900 2245-2245/com.example.androidthings.myproject W/System.err:  at org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:70) 
12-27 15:03:58.900 2245-2245/com.example.androidthings.myproject W/System.err: ... 2 more 

**編輯**
更改IP地址爲127.0.0.1，現在接收不同的錯誤堆棧。我已經更新了上面的錯誤日誌。

---

我的不好... MQTT Broker已經關閉。我認爲我可以在設備上創建代理。然後我意識到它應該在服務器上運行，而我在初始測試期間啓動的服務器已關閉。
當我開始使用Mosquitto中間服務器，我現在可以從Android連接到它：d

Answer 1

如果adb shell然後ping工作就意味着你的Android事情板上有互聯網連接，是最有可能不是你的問題。

望着堆棧跟蹤

client = new MqttClient("tcp://192.168.1.4:1883", "AndroidThingBroker", persistance); 
client.connect(); 

是引發錯誤的代碼，來縮小你可以在你的計算機上創建一個簡單的Android應用程序，甚至只是一個java main方法的問題，並制定出什麼路線問題是。也許這個IP是錯誤的，等等，但它似乎並不是一個Android事件問題（或者至少讓你的代碼像一個Java應用程序一樣工作，以儘量減少可能性）。

我也會刪除此代碼：

catch (Exception e) { 
     e.printStackTrace(); 
    } 

這樣，你是不是捕捉異常 - 你想要的應用程序，以儘快打破，所以你可以看到路由錯誤，而不是方的影響原來的錯誤。