原文地址：http://www.cnblogs.com/harrisonpc/archive/2011/03/31/2001565.html
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 }
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 }
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 }
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 }
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
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
nimei1111
nimei11111111
nimei11111111111111111