Android的網路通訊很多都是基於socket，在這裡說一下簡單的Android的socket通訊的例子。在這裡我們模擬一下群聊。

首先我們瞭解一下什麼是socket，socket又稱“套接字”，應用程式通常通過“套接字”向網路發出請求或者應答請求。在Java中Socket和ServerSocket類庫位於java.net包中。ServerSocket用於伺服器端，Socket是建立網路連結使用的，連線成功後應用程式的兩端都會產生一個Socket例項，操作這個例項，我們就可以完成回話了。

Socket連結建立的過程：

1.伺服器監聽

2.客戶端發出請求

3.建立連結

4.通訊

服務端的程式碼：

package com.example.testmysetversocket.main;

/**
 * 啟動執行緒開始監聽
 * @author Allen
 *
 */
public class MyServerSocket {

	public static void main(String[] args) {
		new ServerListener().start();
		
	}

}

package com.example.testmysetversocket.main;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JOptionPane;
/**
 * 監聽客戶端請求的執行緒類
 * @author Allen
 *
 */
public class ServerListener extends Thread {

	@Override
	public void run() {
		//1-65535
		try {
			ServerSocket serverSocket = new ServerSocket(12345);
			//迴圈監聽來自客戶端的連線
			while (true) {
				//block
				Socket socket = serverSocket.accept();
				//建立連線
				JOptionPane.showMessageDialog(null, "有客戶端連結到了本機的12345埠");
				//將socket傳遞給新的執行緒
				ChatSocket cs = new ChatSocket(socket);
				cs.start();
				ChatManager.getChatManager().add(cs);
			}
			
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}
 

package com.example.testmysetversocket.main;

import java.util.Vector;
/**
 * 管理聊天執行緒的類，每個客戶端只有一個聊天執行緒
 * @author Allen
 *
 */
public class ChatManager {
	//把ChatManager單例化
	private ChatManager(){}
	private static final ChatManager cm = new ChatManager();
	public static ChatManager getChatManager() {
		return cm;
	}
	
	//ChatSocket執行緒管理集合
	Vector<ChatSocket> vector = new Vector<ChatSocket>();
	
	/**
	 * 新增ChatSocket
	 * @param cs
	 */
	public void add(ChatSocket cs) {
		vector.add(cs);
	}
	
	/**
	 * 向其他所有客戶端傳送資訊
	 * @param cs
	 * @param out
	 */
	public void publish(ChatSocket cs,String out) {
		for (int i = 0; i < vector.size(); i++) {
			ChatSocket csChatSocket = vector.get(i);
			//進行判斷，當前傳送資訊的執行緒就不用再接收資訊了
			if (!cs.equals(csChatSocket)) {
				csChatSocket.out(out);
			}
		}
	}
}
 

package com.example.testmysetversocket.main;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.Socket;
/**
 * socket通訊的執行緒類
 * @author Allen
 *
 */
public class ChatSocket extends Thread {
	
	Socket socket;
	/**
	 * 建構函式
	 * @param s
	 */
	public ChatSocket(Socket s){
		this.socket = s;
	}
	/**
	 * 輸出訊息到客戶端
	 * @param out
	 */
	public void out(String out) {
		try {
			socket.getOutputStream().write((out+"\n").getBytes("UTF-8"));
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/**
	 * 從客戶端接收資訊，並把訊息傳送給其他所有的客戶端
	 */
	@Override
	public void run() {
		out("你已經連線到本伺服器了");
		try {
			BufferedReader br = new BufferedReader(
					new InputStreamReader(
							socket.getInputStream(),"UTF-8"));
			String line = null;
			//把訊息傳送給其他所有客戶端
			while ((line = br.readLine()) != null) {
				System.out.println(line);
				ChatManager.getChatManager().publish(this, line);
			}
			//這裡注意要把當前的流關閉
			br.close();
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}

MainActivity佈局檔案

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <EditText
            android:id="@+id/ip"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.6"
            android:hint="輸入伺服器的IP地址"
            android:text="10.0.2.2" >

        </EditText>

        <Button
            android:id="@+id/connect"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.4"
            android:text="連線" />

    </LinearLayout>

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0.86" >

        <TextView
            android:id="@+id/text"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:text="Ready..." />
    </ScrollView>

    <EditText
        android:id="@+id/edit"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="在這裡輸入內容" />

    <Button
        android:id="@+id/send"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="傳送" />

</LinearLayout>

package com.example.mysocketclient;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;

import com.jikexueyuan.mysocketclient.R;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	EditText ip;
	EditText editText;
	TextView text;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		ip = (EditText) findViewById(R.id.ip);
		editText = (EditText) findViewById(R.id.edit);
		text = (TextView) findViewById(R.id.text);

		findViewById(R.id.connect).setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View arg0) {
				connect();
			}
		});

		findViewById(R.id.send).setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View arg0) {
				send();
			}
		});
	}

	//-------------------------------------

	Socket socket = null;
	BufferedWriter writer = null;
	BufferedReader reader = null;
	/**
	 * 建立連結
	 */
	public void connect() {

		
		AsyncTask<Void, String, Void> read = new AsyncTask<Void, String, Void>() {

			@Override
			protected Void doInBackground(Void... arg0) {
				try {
					socket = new Socket(ip.getText().toString(), 12345);
					writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
					reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
					publishProgress("@success");
				} catch (UnknownHostException e1) {
					Toast.makeText(MainActivity.this, "無法建立連結", Toast.LENGTH_SHORT).show();
				} catch (IOException e1) {
					Toast.makeText(MainActivity.this, "無法建立連結", Toast.LENGTH_SHORT).show();
				}
				try {
					String line;
					while ((line = reader.readLine())!= null) {
						publishProgress(line);
					}
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				return null;
			}

			@Override
			protected void onProgressUpdate(String... values) {
				if (values[0].equals("@success")) {
					Toast.makeText(MainActivity.this, "連結成功！", Toast.LENGTH_SHORT).show();
					
				}
				text.append("別人說："+values[0]+"\n");
				super.onProgressUpdate(values);
			}
		};
		read.execute();

	}
	/**
	 * 傳送訊息
	 */
	public void send() {
		try {
			text.append("我說："+editText.getText().toString()+"\n");
			writer.write(editText.getText().toString()+"\n");
			writer.flush();
			editText.setText("");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

}

注意：要加Internet訪問許可權，不然會報錯

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.jikexueyuan.mysocketclient"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="17" />
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.mysocketclient.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>