android socket編程實例

android客戶端通過socket與服務器進行通信可以分為以下幾步：
應用程序與服務器通信可以采用兩種模式：TCP可靠通信 和UDP不可靠通信。
（1）通過IP地址和端口實例化Socket，請求連接服務器：
     socket = new Socket(HOST, PORT);   //host:為服務器的IP地址  port：為服務器的端口號
（2）獲取Socket流以進行讀寫，並把流包裝進BufferWriter或者PrintWriter：
   PrintWriter out = new PrintWriter( new BufferedWriter( new OutputStreamWriter(socket.getOutputStream())),true);  
   這里涉及了三個類：socket.getOutputStream得到socket的輸出字節流，OutputStreamWriter是字節流向字符流轉換的橋梁，BufferWriter是字符流，然后再包裝進PrintWriter。
（3）對Socket進行讀寫

     if (socket.isConnected()) {
                    if (!socket.isOutputShutdown()) {
                        out.println(msg);
                    }
                }

（4）關閉打開的流

  out.close();

在寫代碼的過程中一定要注意對socket  輸入流  輸出流的關閉

下面是一個簡單的例子：
main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:orientation="vertical"
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent">  
    <TextView
        android:id="@+id/TextView"
        android:singleLine="false"  
        android:layout_width="fill_parent"  
        android:layout_height="wrap_content" />  
    <EditText android:hint="content"
        android:id="@+id/EditText01"  
        android:layout_width="fill_parent"  
        android:layout_height="wrap_content">  
    </EditText>  
    <Button
        android:text="send"
        android:id="@+id/Button02"  
        android:layout_width="fill_parent"  
        android:layout_height="wrap_content">  
    </Button>  
</LinearLayout>

下面是android客戶端的源代碼：

package com.android.SocketDemo;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class SocketDemo extends Activity implements Runnable {
    private TextView tv_msg = null;
    private EditText ed_msg = null;
    private Button btn_send = null;
//    private Button btn_login = null;
    private static final String HOST = "192.168.1.223";
    private static final int PORT = 9999;
    private Socket socket = null;
    private BufferedReader in = null;
    private PrintWriter out = null;
    private String content = "";
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tv_msg = (TextView) findViewById(R.id.TextView);
        ed_msg = (EditText) findViewById(R.id.EditText01);
//        btn_login = (Button) findViewById(R.id.Button01);
        btn_send = (Button) findViewById(R.id.Button02);
        try {
            socket = new Socket(HOST, PORT);
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(
                    socket.getOutputStream())), true);
        } catch (IOException ex) {
            ex.printStackTrace();
            ShowDialog("login exception" + ex.getMessage());
        }
        btn_send.setOnClickListener(new Button.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                String msg = ed_msg.getText().toString();
                if (socket.isConnected()) {
                    if (!socket.isOutputShutdown()) {
                        out.println(msg);
                    }
                }
            }
        });
        //啟動線程，接收服務器發送過來的數據
        new Thread(SocketDemo.this).start();
    }
    //如果連接出現異常，彈出AlertDialog！
    public void ShowDialog(String msg) {
        new AlertDialog.Builder(this).setTitle("notification").setMessage(msg)
                .setPositiveButton("ok", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                    }
                }).show();
    }
    //讀取服務器發來的信息，並通過Handler發給UI線程
    public void run() {
        try {
            while (true) {
                if (socket.isConnected()) {
                    if (!socket.isInputShutdown()) {
                        if ((content = in.readLine()) != null) {
                            content += "\n";
                            mHandler.sendMessage(mHandler.obtainMessage());
                        } else {
                        }
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //接收線程發送過來信息，並用TextView顯示
    public Handler mHandler = new Handler() {
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            tv_msg.setText(tv_msg.getText().toString() + content);
        }
    };
}

下面是服務器端得java代碼：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class Main {
    private static final int PORT = 9999;
    private List<Socket> mList = new ArrayList<Socket>();
    private ServerSocket server = null;
    private ExecutorService mExecutorService = null; //thread pool
    
    public static void main(String[] args) {
        new Main();
    }
    public Main() {
        try {
            server = new ServerSocket(PORT);
            mExecutorService = Executors.newCachedThreadPool();  //create a thread pool
            System.out.print("服務器已啟動...");
            Socket client = null;
            while(true) {
                client = server.accept();
                //把客戶端放入客戶端集合中
                mList.add(client);
                mExecutorService.execute(new Service(client)); //start a new thread to handle the connection
            }
        }catch (Exception e) {
            e.printStackTrace();
        }
    }
    class Service implements Runnable {
            private Socket socket;
            private BufferedReader in = null;
            private String msg = "";
            
            public Service(Socket socket) {
                this.socket = socket;
                try {
                    in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                    //客戶端只要一連到服務器，便向客戶端發送下面的信息。
                    msg = "user" +this.socket.getInetAddress() + "come toal:"
                        +mList.size();
                    this.sendmsg();
                } catch (IOException e) {
                    e.printStackTrace();
                }           
            }
            @Override
            public void run() {
                // TODO Auto-generated method stub
                try {
                    while(true) {
                        if((msg = in.readLine())!= null) {
                            //當客戶端發送的信息為：exit時，關閉連接
                            if(msg.equals("exit")) {
                                System.out.println("ssssssss");
                                mList.remove(socket);
                                in.close();
                                msg = "user:" + socket.getInetAddress()
                                    + "exit total:" + mList.size();
                                socket.close();
                                this.sendmsg();
                                break;
                                //接收客戶端發過來的信息msg，然后發送給客戶端。
                            } else {
                                msg = socket.getInetAddress() + ":" + msg;
                                this.sendmsg();
                            }
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
          
           //循環遍歷客戶端集合，給每個客戶端都發送信息。
           public void sendmsg() {
               System.out.println(msg);
               int num =mList.size();
               for (int index = 0; index < num; index ++) {
                   Socket mSocket = mList.get(index);
                   PrintWriter pout = null;
                   try {
                       pout = new PrintWriter(new BufferedWriter(
                               new OutputStreamWriter(mSocket.getOutputStream())),true);
                       pout.println(msg);
                   }catch (IOException e) {
                       e.printStackTrace();
                   }
               }
           }
        }    
}

注意在AndroidManifest.xml中加入對網絡的訪問權限
<uses-permission android:name="android.permission.INTERNET"></uses-permission>

在寫代碼的過程中一定要注意對套接字和輸入/輸出流的關閉

解析：除了isClose方法，Socket類還有一個isConnected方法來判斷Socket對象是否連接成功。  看到這個名字，也許讀者會產生誤解。  其實isConnected方法所判斷的並不是Socket對象的當前連接狀態，  而是Socket對象是否曾經連接成功過，如果成功連接過，即使現在isClose返回true， isConnected仍然返回true。因此，要判斷當前的Socket對象是否處於連接狀態， 必須同時使用isClose和isConnected方法， 即只有當isClose返回false，isConnected返回true的時候Socket對象才處於連接狀態。 雖然在大多數的時候可以直接使用Socket類或輸入輸出流的close方法關閉網絡連接，但有時我們只希望關閉OutputStream或InputStream，而在關閉輸入輸出流的同時，並不關閉網絡連接。這就需要用到Socket類的另外兩個方法：shutdownInput和shutdownOutput，這兩個方法只關閉相應的輸入、輸出流，而它們並沒有同時關閉網絡連接的功能。和isClosed、isConnected方法一樣，Socket類也提供了兩個方法來判斷Socket對象的輸入、輸出流是否被關閉，這兩個方法是isInputShutdown()和isOutputShutdown()。 shutdownInput和shutdownOutput並不影響Socket對象的狀態。

 super.onCreate(savedInstanceState);

        // android3.0以后需要加入以下的代碼，否則會報socket連接異常的錯誤
        StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectDiskReads().detectDiskWrites().detectNetwork().penaltyLog().build()); 
        StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectLeakedSqlLiteObjects().penaltyLog().penaltyDeath().build());  

        setContentView(R.layout.activity_login);