<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 tools:context=".MainActivity" >
 <EditText 
  android:id="@+id/et_text"
  android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:layout_alignParentTop="true"
  android:hint="請填入要發送的內容"
  />
  <Button 
  android:id="@+id/btn_send"
  android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentRight="true"
   android:layout_below="@+id/et_text"
  android:text="發送"
  />
  <TextView 
   android:id="@+id/tv_recv"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:layout_below="@+id/btn_send"
   android:minLines="20"
   android:hint="接收的內容"
   />
</RelativeLayout>

package com.example.tcpdemo;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
 TcpThread mt;
 TextView tv_recv;
 EditText et_text;  //要發送的內容
 Button btn_send;
 //定義一個handler
 public Handler mHandler = new Handler() {
  public void handleMessage(Message msg) {
   //打印服務器端發來的消息
   System.out.println("read:"+msg.obj.toString());
   tv_recv.append(msg.obj.toString()+"\r\n");
  };
 };
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  tv_recv = (TextView)findViewById(R.id.tv_recv);
  et_text = (EditText)findViewById(R.id.et_text);
  mt = new TcpThread();
  mt.setHandler(mHandler); //設置handler
  mt.setIp("10.10.10.104"); //設置服務器地址
  mt.start();     //啟動線程
  btn_send = (Button)findViewById(R.id.btn_send);
  btn_send.setOnClickListener(new OnClickListener() {
   //向服務器端發送數據
   public void onClick(View v) {
    if(!mt.write(et_text.getText().toString()))
    {
     Toast.makeText(getApplicationContext(), "發送失敗", Toast.LENGTH_SHORT).show();
    }
   }
  });
 }
}

package com.example.tcpdemo;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import android.os.Handler;
import android.os.Message;
public class TcpThread extends Thread {
  
  Handler mHandler=null; 
  Socket socket = null;
  String ip = null;
  OutputStream outputStream = null;  //輸出流
  InputStream inputStream=null;   //接收流
  //獲取另一個線程的Handler
  public void setHandler( Handler handler){
   mHandler = handler;
  }
  //設置服務器IP
  public void setIp(String ip){
   this.ip = ip;
  }
  public void run(){
   try {
     socket = new Socket(ip, 8080);  //訪問指定的ip地址:8080
    } catch (UnknownHostException e) { 
     e.printStackTrace();
    } catch (IOException e) { 
     e.printStackTrace();
    }
   
   //獲取輸出流
   try {
    outputStream = socket.getOutputStream();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   } 
   try{
    while (true)   //讀取服務器端發送來的數據
    {
     final byte[] buffer = new byte[1024];//創建接收緩沖區
     inputStream = socket.getInputStream();
     final int len = inputStream.read(buffer);//數據讀出來，并且返回數據的長度
     if(len>0)
     {
       Message msg = mHandler.obtainMessage(); 
       //設置發送的內容
       msg.obj = new String(buffer,0,len); 
       mHandler.sendMessage(msg); 
     }
    }
   }
   catch (IOException e) {
   }
  }
  //向服務器端寫入數據
  public boolean write(String text){
   boolean ret = true;
   try {
    outputStream.write(text.toString().getBytes());
   } catch (IOException e) { 
    ret = false;
    e.printStackTrace();
   }
   return ret;
  }
}