为什么此代码会与“套接字设置捕获的IOexception”一起循环

Question

I am trying to troubleshoot an Android server/client set of software which appears to be logging vast amounts of logcat messages containing "Socket setup caught IOexception", so Im guessing its in a loop. For troubleshooting purposes I installed the server and client on the same physical device and experience the same problem. Reading the code I cant work out why this would be, I have added comments starting //STACKEXCHANGE where I see the three logcat messages getting logged. Could anyone give me some pointers, Im not a java programmer, just an enthusiastic techie trying to get this working..

The logcat logs the messages in the following order

ControlLooop starting Socket setup caught IOexception Socket Established Socket Closing controlLoopEnding

And here is the code for the client software.

    package com.jrbowling.robotclient;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.util.Log; 
import android.widget.ToggleButton;
import android.widget.SeekBar;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.Toast;
import android.widget.EditText;
import android.widget.ImageView;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.view.Window;
import android.view.WindowManager;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException; 
import java.net.SocketTimeoutException;
import android.net.wifi.WifiManager;
import android.net.wifi.WifiManager.WifiLock;
import android.net.wifi.WifiInfo;  
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.view.View.OnTouchListener;
import android.view.MotionEvent;
import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException; 
import java.net.SocketTimeoutException;
import android.app.AlertDialog;
import android.content.DialogInterface;
import java.net.SocketAddress;
import java.net.InetSocketAddress;
import android.os.Handler;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;

public class MainActivity extends Activity {

    Thread vidThread = null;
    Thread clientThread = null;
    private Socket s;

    private static final String TAG = "RobotClient";
    //private ToggleButton tb;
    private ImageButton forward_button;
    private ImageButton reverse_button;
    private ImageButton right_button;
    private ImageButton left_button;
    private SeekBar throttle;

    private ImageView imageWindow;
    private ImageView connectedLED;
    private ImageView signalStrengthIndicator;

    private Boolean stayConnected = false;
    String vidURL = "";
    private String robotIP = "";
    String direction = "stop";
    Integer speed = 100;
    Boolean robotEnabled = true;
    Boolean robotConnected = false;
    private Handler GUIUpdateHandler = new Handler();
    private Integer signalStrength = 0;
    private SharedPreferences pref; 
    private long timeLastPress = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //set fullscreeen, black
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
        WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_main);
        setActivityBackgroundColor(0xff000000);

        Log.i(TAG, "Robot client started"); 

        initGUIComponents();

        //get Robot IP from user, kick off threads and GUI updater
        showIPAlert();  

    }

@Override
 protected void onDestroy() {

     Log.d(TAG,"onDestroy() called");
     stayConnected = false;
     socketCleanup();
     super.onDestroy(); 

    }

//@Override
//protected void onPause() {

//   Log.d(TAG,"onPause() called");
//   stayConnected = false;
//   socketCleanup();
//   super.onDestroy();
//   }

@Override
 public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

@Override
 public void onBackPressed() {
        //on back button, prompt user to press it again within 2 seconds to exit
        Toast onBackPressedToast = Toast.makeText(this, "Press again within 2 seconds to confirm exit", Toast.LENGTH_SHORT);
        long currentTime = System.currentTimeMillis();
        if (currentTime - timeLastPress > 2000) {
            onBackPressedToast.show();
            timeLastPress = currentTime;
        } else {
            onBackPressedToast.cancel();  
            super.onBackPressed();           
        }
    }

 private void initGUIComponents()
    {
        imageWindow = (ImageView) findViewById(R.id.imageView1);
        connectedLED = (ImageView) findViewById(R.id.imageViewConnectStatus);
        signalStrengthIndicator  = (ImageView) findViewById(R.id.ImageViewSignalStrength);
        forward_button = (ImageButton) findViewById(R.id.forwardButton);
        reverse_button = (ImageButton) findViewById(R.id.reverseButton);
        right_button = (ImageButton) findViewById(R.id.rightButton);
        left_button = (ImageButton) findViewById(R.id.leftButton);
        throttle = (SeekBar)findViewById(R.id.throttleSeekbar);
        throttle.setProgress(75); 
        forward_button.setOnTouchListener(forwardButtonListener);
        reverse_button.setOnTouchListener(reverseButtonListener);
        right_button.setOnTouchListener(rightButtonListener);
        left_button.setOnTouchListener(leftButtonListener);
    }

    private void showIPAlert() {

        AlertDialog.Builder alert = new AlertDialog.Builder(this);

        alert.setTitle("Please enter robot IP address");
        alert.setMessage("Example: 192.168.1.100");

        final EditText input = new EditText(this);
        alert.setView(input);
        input.setText(loadIP().toString());

        alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
            robotIP = input.getText().toString();
            Log.i(TAG, "User entered IP " + robotIP);
            saveIP(robotIP);
            //Handler launches GUIUpdater every 1000 ms. Launch when user clicks ok.
            updateGUI();

            //start network thread
            stayConnected = true;

            //launch network thread
            clientThread = new Thread(new ClientThread());
            clientThread.start();

            vidURL = "http://"+robotIP+":8082/shot.jpg";
            vidLoop();
          }
        });

        alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton) {
              appExit();
          }

        });

        alert.show();   
    }

 private void appExit() 
 {
     Log.i(TAG, "Exit requested by user");
     this.finish();  
 }

 private OnTouchListener forwardButtonListener = new OnTouchListener(){
        public boolean onTouch(View v, MotionEvent event) {
           switch ( event.getAction() ) {
            case MotionEvent.ACTION_DOWN: 
                //setActivityBackgroundColor(0xffff0000);
                direction = "forward";
                 break;
            case MotionEvent.ACTION_UP: 
                //setActivityBackgroundColor(0xff000000);
                direction = "stop";
                 break;
            }
           return false;
        }  
   };

 private OnTouchListener reverseButtonListener = new OnTouchListener(){
       public boolean onTouch(View v, MotionEvent event) {
          switch ( event.getAction() ) {
           case MotionEvent.ACTION_DOWN: 
            //setActivityBackgroundColor(0xffff0000);
            direction = "reverse";
             break;
           case MotionEvent.ACTION_UP: 
            //setActivityBackgroundColor(0xff000000);
            direction = "stop";
             break;
           }
          return false;
       }  
  };

 private OnTouchListener rightButtonListener = new OnTouchListener(){
      public boolean onTouch(View v, MotionEvent event) {
         switch ( event.getAction() ) {
          case MotionEvent.ACTION_DOWN: 
            //setActivityBackgroundColor(0xffff0000);
            direction = "rotateRight";
             break;
          case MotionEvent.ACTION_UP: 
            //setActivityBackgroundColor(0xff000000);
            direction = "stop";
             break;
          }
         return false;
      }  
 };

 private OnTouchListener leftButtonListener = new OnTouchListener(){
     public boolean onTouch(View v, MotionEvent event) {
        switch ( event.getAction() ) {
         case MotionEvent.ACTION_DOWN: 
            //setActivityBackgroundColor(0xffff0000);
            direction = "rotateLeft";
             break;
         case MotionEvent.ACTION_UP: 
            //setActivityBackgroundColor(0xff000000);
            direction = "stop";
             break;
         }
        return false;
     }  
};


//save and retrieve IP address using the shared preferences framework
 private void saveIP(String IP)
 {
    //set up shared preferences editor
     pref = getApplicationContext().getSharedPreferences("RobotClient", 0); 
     Editor editor = pref.edit();
     editor.putString("robotIP", IP); 
     editor.commit();
 }

 private String loadIP()
 {
 String result;

 pref = getApplicationContext().getSharedPreferences("RobotClient", 0); 
 Editor editor = pref.edit();
 result = pref.getString("robotIP", "10.20.30.43");

 return result;
 }

 private void setActivityBackgroundColor(int color) {
        //0xff00ff00  first two are transparency, then rgb

        View view = this.getWindow().getDecorView();
        view.setBackgroundColor(color);
    }

 //periodically run updater to set connection status and wifi signal strength from robot
 private void updateGUI()
    {
        GUIUpdateHandler.postDelayed(GUIUpdater, 1000);
    }

 private Runnable GUIUpdater = new Runnable(){

        public void run() {
            //Periodically update GUI elements from sensor and other data
            Log.d(TAG,"Connected is: " + robotConnected.toString());

            //update connection status
            if (robotConnected)
            {
                connectedLED.setImageResource(R.drawable.led_green);

                //update the wifi signal strength indicator
                if ((signalStrength == 5) || (signalStrength==4))
                    signalStrengthIndicator.setImageResource(R.drawable.wifi4);

                if (signalStrength == 3) 
                        signalStrengthIndicator.setImageResource(R.drawable.wifi3);

                if (signalStrength == 2) 
                    signalStrengthIndicator.setImageResource(R.drawable.wifi2);

                if (signalStrength == 1) 
                    signalStrengthIndicator.setImageResource(R.drawable.wifi1);

                if (signalStrength == 0) 
                    signalStrengthIndicator.setImageResource(R.drawable.wifi0);
            }

            else
                {
                connectedLED.setImageResource(R.drawable.led_red);
                signalStrengthIndicator.setImageResource(R.drawable.wifi0);
                }

            if (stayConnected)          
                updateGUI();
        }

    };

 public void setConnected(boolean connected) {

    robotConnected = connected;
    }

 public void socketCleanup()
    {
        try {
        Log.d("clientThread","Socket Closing");
        if (s != null)
            s.close();
        setConnected(false);
        } catch (IOException e) {

        Log.d(TAG, "Client comm thread got IOException in socketCleanup().");
        }       
    }

 private void vidLoop() //started from GUI alert, then kept going with call me from asynctask
    {
        if (stayConnected)
            {
            ImageDownloader id = new ImageDownloader();
            id.execute(vidURL); 
            }
    }

    //this very useful chunk of code is from http://www.peachpit.com/articles/article.aspx?p=1823692&seqNum=3
 private class ImageDownloader extends AsyncTask<String, Integer, Bitmap>{
    protected void onPreExecute(){

        }
        @Override
        protected Bitmap doInBackground(String... params) {
            //TODO Auto-generated method stub
            try{
                URL url = new URL(params[0]);
                HttpURLConnection httpCon = 
                (HttpURLConnection)url.openConnection();
                if(httpCon.getResponseCode() != 200)
                    throw new Exception("Failed to connect");
                InputStream is = httpCon.getInputStream();
                return BitmapFactory.decodeStream(is);
            }catch(Exception e){
                Log.e("Image","Failed to load image",e);
            }
            return null;
        } 

        protected void onProgressUpdate(Integer... params){
            //Update a progress bar here, or ignore it, it's up to you
        }
        protected void onPostExecute(Bitmap img){
            ImageView iv = (ImageView)findViewById(R.id.imageView1);
            if(iv!=null && img !=null){
                iv.setImageBitmap(img);
                //start next image grab
                vidLoop();
            }
        }
            protected void onCancelled(){
            }
        }

class ClientThread implements Runnable {

        private static final int SERVERPORT = 8082;

        public void run() {
            Log.d("clientThread","clientThread started");
            setConnected(false);

            while ((!Thread.currentThread().isInterrupted()) && stayConnected)
            {
            controlLoop();
            }

            //user requested disconnect
            Log.d("clientThread","clientThread ending");
        }

        void controlLoop()
        {
            BufferedReader s_input = null;
            PrintWriter s_output = null;
            String inputString = null;
            String outputString = null;
            Boolean continueLoop = true;

            Log.d("clientThread","controlLoop starting");

             //protocol:
            //Java boolean: enabled or disabled 
            //Directions: stop, rotateRight, rotateLeft, forward, reverse
            //Client sends: robotEnabled,direction,servoPanValue
            //Server replies: sensor1,sensor2...

            continueLoop = true;

            try {

                InetAddress serverAddr = InetAddress.getByName(robotIP);
                Socket s = new Socket();
                //int timeout = 2000;   // DEFAULT milliseconds
                int timeout = 6000;   // milliseconds
                SocketAddress sockaddr = new InetSocketAddress(serverAddr, SERVERPORT);
                s.connect(sockaddr, timeout);

                s_input = new BufferedReader(new InputStreamReader(s.getInputStream()));
                s_output = new PrintWriter(s.getOutputStream(), true);

                } catch (UnknownHostException e1) {
                    e1.printStackTrace();
                    Log.d("clientThread","Got invalid IP string in client thread");
                    continueLoop = false;
                } catch (IOException e) {
                        Log.d("clientThread","Socket setup caught IOexception");
                        continueLoop = false;
//STACKEXCHANGE - THIS SEEMS TO BE WHERE THE CODE REPEATEDLY LOOPS AROUND TRYING TO CONNECT**********************************************************************************************
                    }
//STACKEXCHANGE - Loop starts below again and then logging "controlloop ending"
            Log.d("clientThread","Socket Established");

            setConnected(true);

            try {

                while ((stayConnected) && (continueLoop)) { 

                    speed = throttle.getProgress();

                    if (stayConnected)
                        outputString = robotEnabled.toString() + "," + direction.toString() + "," + speed.toString(); 
                    else 
                        outputString = "quit";

                    s_output.println(outputString);

                    if (!s_output.checkError())
                        {
                        inputString = s_input.readLine();

                        if (inputString == null)
                            {
                            continueLoop = false;
                            Log.d("clientThread","Unexpected disconnection.");
                            }
                        else
                        {
                        Log.d("clientThread","Client got: " + inputString.toString());
                        //parse returned string, which is just an integer containing the signal strength
                        try {
                            signalStrength = Integer.parseInt(inputString);
                            } catch(NumberFormatException nfe) {
                                Log.d(TAG,"Got invalid signal strength from client");
                            } 
                            }
                        }
                    else
                        {
                        //printwriter.checkError returned true, something bad happened network-wise
                        continueLoop = false;
                        Log.d("clientThread","Printwriter.checkError() returned true, likely network problem");
                        }
                }

             socketCleanup();
             Log.d("clientThread","controlLoop ending");
             //STACKEXCHANGE - This is also logged in the catlog at the end of repetitive loop
            } catch (IOException e) {
                //this happens if the connection times out.
                Log.d("clientThread", "Client comm thread got IOException in control loop.");
                socketCleanup();
            }    

        }//end control loop

    } //end client thread

}

Answer 1

It's because you don't modify stayConnected. You continually call

while ((!Thread.currentThread().isInterrupted()) && stayConnected)
{
    controlLoop();
}

and get an exception each time with your call. Only modifying continueLoop to false. You should break your while on that condition or interrupt your thread as well for your intended behavior; or some other approach would work.