首先，创建一个服务器端的套接字，并规定套接字监听的端口：

ServerSocket serverSocket = new ServerSocket(8001);

然后，等待客户端通过端口8001的请求：

Socket socket=serverSocket.accept();

接下来创建客户端接收到的套接字的输入输出流，并将输入输出流转化成扫描器和写入器：

InputStream inputStream = incomingSocket.getInputStream();

OutputStream outputStream = incomingSocket.getOutputStream();

//将输入流转化为扫描器，输出流转化为写入器

Scanner inScanner=new Scanner(inputStream);

PrintWriter outPrintWriter= new PrintWriter(outputStream, true);

接下来就可以运用扫描器获得客户端传来的数据，并运用写入器将传来的数据发送给客户端：

String backString=inScanner.next();

outPrintWriter.println("you give me:"+backString);

然后，将每一个连接创建一个新的线程，独立运行。

运用命令行的telnet命令就可以连接上客户端：

可以多次创建连接：

一下为完整代码：

package server;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.Scanner;

public class ThreadEchoServer {

public static void main(String[] args) {

// TODO Auto-generated method stub

try {

int i=1;

ServerSocket serverSocket = new ServerSocket(8001);

while(true){

//等待客户端通过端口8001请求的连接

Socket socket=serverSocket.accept();

System.out.println("spawning"+i);

Runnable runnable= new ThreadEchoHandler(socket);

Thread thread = new Thread(runnable);

thread.start();

i++;

}

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

class ThreadEchoHandler implements Runnable

{

private Socket incomingSocket;

public ThreadEchoHandler(Socket in){

incomingSocket=in;

}

public void run(){

try {

try {

//建立套接字的输入输出流

InputStream inputStream = incomingSocket.getInputStream();

OutputStream outputStream = incomingSocket.getOutputStream();

//将输入流转化为扫描器，输出流转化为写入器

Scanner inScanner=new Scanner(inputStream);

PrintWriter outPrintWriter= new PrintWriter(outputStream, true);

//运用写入器的println函数向客户端输出字符串

outPrintWriter.println("welcome!");

//将客户端传输的数据发送回去，如果客户端输入的数据为bye，则断开连接

boolean flag=false;

while(!flag&&inScanner.hasNext()){

String backString=inScanner.next();

outPrintWriter.println("you give me:"+backString);

if(backString.trim().equals("bye")){

flag=true;

}

}

} finally {

// TODO: handle exception

//关闭套接字(很重要，防止造成资源浪费)

incomingSocket.close();

}

} catch (IOException e) {

// TODO: handle exception

}

}

}

本文参考《Java核心技术卷II》