服務端：

package com.chinasofti.corejava.ch22;

import java.io.BufferedReader;
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.Scanner;


public class Server {
	private static BufferedReader br=null;
	private static PrintWriter pw=null;
	private static ServerSocket ss;
	private static Socket s;
	static Scanner scanner=new Scanner(System.in);
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try {
			ss=new ServerSocket(5500);
			System.out.println("服務器正常啟動。。。。");
		    s=ss.accept();//阻塞方法
		    System.out.println("連接成功"+s.getRemoteSocketAddress());
		    br=new BufferedReader(new InputStreamReader(s.getInputStream()));
			pw=new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
			while(true){
				String string=br.readLine();
				System.out.println("Server讀到："+string);
				System.out.println("Server端請輸入：");
				String str=scanner.next();
				pw.println(str);
				pw.flush();
				if(str.equals("exit")){
					break;
				}
			}
		} catch (Exception e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
		}
		try {
			pw.close();
			br.close();
		} catch (IOException e1) {
				// TODO Auto-generated catch block
			e1.printStackTrace();
		}
	}

}　
端口：

package com.chinasofti.corejava.ch22;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;


public class Client {
	private static PrintWriter pw=null;
	private static BufferedReader br=null;
	private static Socket s;
	static Scanner scanner=new Scanner(System.in);
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try {
			Socket s=new Socket(InetAddress.getLocalHost(),5500);
			pw=new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
			br=new BufferedReader(new InputStreamReader(s.getInputStream()));
			while(true){
				System.out.println("Client端請輸入：");
				String str = scanner.next();
				pw.println(str);
				pw.flush();
				String string=br.readLine();
				System.out.println("Client讀到："+string);
				if(str.equals("exit")){
					break;
				}
			} 
		}catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
		}
		try {
			br.close();
			pw.close();
		} catch (IOException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
		}
	}
}

星期三—用JAVA制作簡易的通訊軟件