MainActivity

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.view.View;
import android.view.Window;
import android.view.View.OnClickListener;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.ImageButton;

import com.example.hfut.ClientService.ClientCallback;

public class MainActivity extends Activity implements ClientCallback {

private ImageButton w = null;
private ClientService client_service = new ClientService();
private ClientService.MsgBinder binder = null;
private boolean is_bind = false;
private Handler handler = null;
private CSConnection csconn = null;
private String ip = null;
private String port = null;
private int i = 0;
private final int START_ANIM = 0x1;

@SuppressLint("HandlerLeak")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
    setContentView(R.layout.activity_main);
    initViews();

    Intent intent = getIntent();
    ip = intent.getStringExtra("ip");
    port = intent.getStringExtra("port");
    i = Integer.parseInt(port);
    // System.out.println("binder1----------->" + binder);
    new Thread() {
        public void run() {
            client_service.initSocket(ip, i);
            startCustomService();
            System.out.println("binder2----------->" + binder);
        }
    }.start();
    startCustomService();
    w.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // startCustomService();
            System.out.println("binder3----------->" + binder);
            binder.sendText("w");  //此处不能发送
            System.out.println("w----------->" + w);
        }
    });
}

private void initViews() {
    w = (ImageButton) findViewById(R.id.w);
}

ServiceConnection conn = new ServiceConnection() {
    @Override
    public void onServiceDisconnected(ComponentName name) {
        is_bind = false;
    }


    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        binder = (ClientService.MsgBinder) service;
        client_service = (ClientService) binder.getSevice();
        client_service.setCallback(MainActivity.this);
        is_bind = true;
    }
};

private void startCustomService() {
    Intent intent = new Intent(this, ClientService.class);
    bindService(intent, conn, Context.BIND_AUTO_CREATE);
}

private void stopCutomService() {
    if (is_bind) {
        unbindService(conn);
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();
    stopCutomService();
}

@Override
public void runAnimation() {
    handler.sendEmptyMessage(START_ANIM);
}

}

ClientService

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;

import android.app.Service;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Binder;
import android.os.IBinder;
import android.widget.Toast;

public class ClientService extends Service {

private static Socket socket = null;
private static PrintWriter out = null;
private ClientCallback client_callback = null;
private Drawable drawable = null;
private boolean is_need_stop = false;

@Override
public IBinder onBind(Intent intent) {
    IBinder result = null;
    if (null == result)
        result = new MsgBinder();
    Toast.makeText(this, "onBind", Toast.LENGTH_LONG).show();
    return result;
}

@Override
public void onCreate() {
    super.onCreate();
    System.out.println("onCreate.....");
    Toast.makeText(this, "onCreate", Toast.LENGTH_LONG).show();
}

@Override
public void onDestroy() {
    super.onDestroy();
    if (socket != null) {
        try {
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    is_need_stop = true;
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    return super.onStartCommand(intent, flags, startId);
}

public void setCallback(ClientCallback clientcallback) {
    this.client_callback = clientcallback;
}

public void initSocket(String s, int i) {
    try {
        if (socket != null) {
            socket.close();
            socket = null;
        }
        socket = new Socket(s, i);
        out = new PrintWriter(socket.getOutputStream(), true);
        System.out.println("socket------->" + socket);
        System.out.println("out------->" + out);
    } catch (IOException ex) {
        ex.printStackTrace();

    }
}

// private void startAnim() {
// if (client_callback == null) {
// return;
// }
// client_callback.runAnimation();
// }

// private void releaseLastSocket(Socket mSocket) {
// try {
// if (null != mSocket) {
// if (!mSocket.isClosed()) {
// mSocket.close();
// }
// mSocket = null;
// }
// } catch (IOException e) {
// e.printStackTrace();
// }
// }

public class MsgBinder extends Binder {
    public Service getSevice() {
        return ClientService.this;
    }

    public void sendText(String text) {
        if (socket == null) {
            System.out.println("socket-null------->" + socket);
            System.out.println("out-null-------->" + out);
            return;
        }
        if (socket.isConnected()) {
            if (!socket.isOutputShutdown()) {
                System.out.println("socket-notnull------->" + socket);
                out.print(text);
                System.out.println("out-notnull-------->" + out);
                out.flush();
            }
        }
    }

    public boolean sendMsg(String msg) {
        if (null == socket) {
            return false;
        }
        try {
            if (!socket.isClosed() && !socket.isOutputShutdown()) {
                OutputStream os = socket.getOutputStream();
                String message = msg;
                os.write(message.getBytes());
                os.flush();
            } else {
                return false;
            }
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    public void receive() {
        stop();
    }

    public void stop() {
        if (socket.isConnected()) {
            if (!socket.isOutputShutdown()) {
                out.println("exit");
                out.flush();
            }
        }
    }
}

interface ClientCallback {

    public void runAnimation();

}

}
#Service已经在Mainfest里面绑定了

 new Thread() {
        public void run() {
            client_service.initSocket(ip, i);//这里的client_service是你自己new出来的，private ClientService client_service = new ClientService(); 不是ServiceConnection返回的。这时候你的service还没启动呢，怎么可能能设置呢。所以这段代码有问题，先启动service，在初始化socket 也就是把这段线程启动放到onServiceConnected里面去初始化socket。
            startCustomService();
            System.out.println("binder2----------->" + binder);
        }
    }.start();
    startCustomService();