1 import java.io.IOException;
 2 import java.net.ServerSocket;
 3 import java.net.Socket;
 4 import java.util.ArrayList;
 5
 6 public class Server {
 7
 8     private static ArrayList<Socket> list = new ArrayList<Socket>();
 9     public static void main(String[] args) throws IOException {
10         ServerSocket server = new ServerSocket(9999);
11         while(true){
12             Socket socket = server.accept();
13             list.add(socket);
14             new ServerThread(socket,list).start();;
15         }
16
17     }
18
19
20
21 }

 1 import java.io.IOException;
 2 import java.net.Socket;
 3 import java.net.UnknownHostException;
 4
 5 public class Client {
 6
 7     public static void main(String[] args) throws UnknownHostException, IOException {
 8         Socket socket = new Socket("127.0.0.1",9999);
 9         new ThreadWriter(socket).start();
10         new ThreadReader(socket).start();
11     }
12
13 }

 1 import java.io.IOException;
 2 import java.io.InputStream;
 3 import java.io.OutputStream;
 4 import java.net.Socket;
 5 import java.util.ArrayList;
 6
 7 public class ServerThread extends Thread {
 8
 9     Socket socket;
10     ArrayList<Socket> list;
11     InputStream is;
12     OutputStream os;
13     public ServerThread(Socket socket, ArrayList<Socket> list) {
14         this.socket = socket;
15         this.list = list;
16     }
17
18     @Override
19     public void run() {
20         try {
21             while(true){
22                 is = socket.getInputStream();
23                 byte[] b = new byte[1024];
24                 int len = is.read(b);
25                 String str = new String(b,0,len);
26                 System.out.println(str);
27                 for(Socket socket:list){
28                     os = socket.getOutputStream();
29                     os.write(str.getBytes());
30                 }
31             }
32
33         } catch (IOException e) {
34             e.printStackTrace();
35         }
36     }
37
38 }

 1 import java.io.IOException;
 2 import java.io.InputStream;
 3 import java.net.Socket;
 4
 5 public class ThreadReader extends Thread {
 6
 7     Socket socket;
 8     public ThreadReader(Socket socket) {
 9         this.socket = socket;
10     }
11
12     @Override
13     public void run() {
14         try {
15             while(true){
16
17                 InputStream is = socket.getInputStream();
18                 byte[] b = new byte[1024];
19                 int len = is.read(b);
20                 String str = new String(b,0,len);
21                 System.out.println(str);
22             }
23         } catch (IOException e) {
24             // TODO Auto-generated catch block
25             e.printStackTrace();
26         }
27     }
28
29 }

 1 import java.io.IOException;
 2 import java.io.OutputStream;
 3 import java.net.Socket;
 4 import java.util.Scanner;
 5
 6 public class ThreadWriter extends Thread {
 7
 8     Socket socket;
 9     public ThreadWriter(Socket socket) {
10         this.socket = socket;
11     }
12
13     @Override
14     public void run() {
15         try {
16             Scanner sc = new Scanner(System.in);
17             while(true){
18                 String str = sc.next();
19                 OutputStream os = socket.getOutputStream();
20                 os.write(str.getBytes());
21             }
22         } catch (IOException e) {
23             // TODO Auto-generated catch block
24             e.printStackTrace();
25         }
26     }
27
28 }