Socket通常也称做”套接字“，用于描述IP地址和端口，废话不多说，它就是网络通信过程中端点的抽象表示。值得一提的是，Java在包java.net中提供了两个类Socket和ServerSocket，分别用来表示双向连接的客户端和服务端。这是两个封装得非常好的类，使用起来很方便！

下面将首先创建一个SocketServer的类作为服务端如下，该服务端实现了多线程机制，可以在特定端口处监听多个客户请求，一旦有客户请求，Server总是会创建一个服务纯种来服务新来的客户，而自己继续监听。程序中accept()是一个阻塞函数，所谓阻塞性方法就是说该方法被调用后将等待客户的请求，直到有一个客户启动并请求连接到相同的端口，然后accept()返回一个对应于客户的Socket。这时，客户方和服务方都建立了用于通信的Socket，接下来就是由各个Socket分别打开各自的输入、输出流。

• SocketServer类，服务器实现：

 1 package HA.Socket;

 2

 3 import java.io.*;

 4 import java.net.*;

 5

 6  public class SocketServer {

 7

 8     ServerSocket sever;

 9

10     public SocketServer(int port){

11         try{

12             sever = new ServerSocket(port);

13         }catch(IOException e){

14             e.printStackTrace();

15         }

16     }

17

18     public void beginListen(){

19         while(true){

20             try{

21                 final Socket socket = sever.accept();

22

23                 new Thread(new Runnable(){

24                     public void run(){

25                         BufferedReader in;

26                         try{

27                             in = new BufferedReader(new InputStreamReader(socket.getInputStream(),"UTF-8"));

28                             PrintWriter out = new PrintWriter(socket.getOutputStream());

29                             while (!socket.isClosed()){

30                                 String str;

31                                 str = in.readLine();

32                                 out.println("Hello!world!! " + str);

33                                 out.flush();

34                                 if (str == null || str.equals("end"))

35                                     break;

36                                 System.out.println(str);

37                             }

38                             socket.close();

39                         }catch(IOException e){

40                             e.printStackTrace();

41                         }

42                     }

43                 }).start();

44             }catch(IOException e){

45                 e.printStackTrace();

46             }

47         }

48     }

49 }

• SocketClient类，客户端实现：

 1 package HA.Socket;

 2

 3 import java.io.*;

 4 import java.net.*;

 5

 6  public class SocketClient {

 7     static Socket client;

 8

 9     public SocketClient(String site, int port){

10         try{

11             client = new Socket(site,port);

12             System.out.println("Client is created! site:"+site+" port:"+port);

13         }catch (UnknownHostException e){

14             e.printStackTrace();

15         }catch (IOException e){

16             e.printStackTrace();

17         }

18     }

19

20     public String sendMsg(String msg){

21         try{

22             BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));

23             PrintWriter out = new PrintWriter(client.getOutputStream());

24             out.println(msg);

25             out.flush();

26             return in.readLine();

27         }catch(IOException e){

28             e.printStackTrace();

29         }

30         return "";

31     }

32     public void closeSocket(){

33         try{

34             client.close();

35         }catch(IOException e){

36             e.printStackTrace();

37         }

38     }

39     public static void main(String[] args) throws Exception{

40

41     }

42

43 }

接下来就是来测试Socket通信了！

先运行TestSocketServer类，打开服务端，在12345端口处监听！

1 package HA.Socket;

2

3  public class TestSocketServer {

4

5     public static void main(String[] argvs){

6         SocketServer server = new SocketServer(12345);

7         server.beginListen();

8     }

9 }

再运行TestSocketClient类：

 1 package HA.Socket;

 2

 3  public class TestSocketClient {

 4

 5     public static void main(String[] args){

 6

 7         SocketClient client = new SocketClient("127.0.0.1",12345);

 8         System.out.println(client.sendMsg("nimei1"));

 9         client.closeSocket();

10

11         SocketClient client1 = new SocketClient("127.0.0.1",12345);

12         System.out.println(client1.sendMsg("nimei1111"));

13         client1.closeSocket();

14

15         SocketClient client11 = new SocketClient("127.0.0.1",12345);

16         System.out.println(client11.sendMsg("nimei11111111"));

17         client11.closeSocket();

18

19         SocketClient client111 = new SocketClient("127.0.0.1",12345);

20         System.out.println(client111.sendMsg("nimei11111111111111111"));

21         client111.closeSocket();

22

23     }

24 }

输出结果如下：

服务端：

Client is created! site:127.0.0.1 port:12345

Hello!world!! nimei1

Client is created! site:127.0.0.1 port:12345

Hello!world!! nimei1111

Client is created! site:127.0.0.1 port:12345

Hello!world!! nimei11111111

Client is created! site:127.0.0.1 port:12345

Hello!world!! nimei11111111111111111

客户端：

nimei1

nimei1111

nimei11111111

nimei11111111111111111