客户端：

1.连接服务器Socket

2.发送消息

服务端：

1.建立服务端口ServerSocket

2.等待用户的连接accept

3.接收用的消息

==========================

package com.wuming.lesson02;import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;//服务端
public class TcpServer03 {public static void main(String[] args) {ServerSocket serverSocket=null;Socket socket=null;InputStream is=null;ByteArrayOutputStream baos=null;//1.提供地址try {serverSocket = new ServerSocket(9999);while(true){//2.连客户端socket = serverSocket.accept();//3.读客户端消息is = socket.getInputStream();/**      byte[] buffer = new byte[1024];int len;while((len=is.read(buffer))!=-1){java.lang.String msg = new java.lang.String(buffer, 0, len);System.out.println(msg);}* *///管道流baos = new ByteArrayOutputStream();byte[] buffer = new byte[1024];int len;while((len=is.read(buffer))!=-1){baos.write(buffer,0,len);}System.out.println(baos.toString());}} catch (IOException e) {e.printStackTrace();}finally {//关闭资源if (baos!=null){try {baos.close();} catch (IOException e) {e.printStackTrace();}}if(is!=null){try {is.close();} catch (IOException e) {e.printStackTrace();}}if(socket!=null){try {socket.close();} catch (IOException e) {e.printStackTrace();}}if(serverSocket!=null){try {serverSocket.close();} catch (IOException e) {e.printStackTrace();}}}}
}
=========================

package com.wuming.lesson02;import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;//客户端
public class TcpClientDemo01 {public static void main(String[] args) {OutputStream os=null;Socket socket=null;//1.服务器地址try {InetAddress serverIp = InetAddress.getByName("127.0.0.1");int port=9999;//2.创socket连接socket = new Socket(serverIp,port);//3.发送消息IO流os = socket.getOutputStream();os.write("你好".getBytes());} catch (Exception e) {e.printStackTrace();}finally {if(os!=null){try {os.close();} catch (IOException e) {e.printStackTrace();}}if(socket!=null){try {socket.close();} catch (IOException e) {e.printStackTrace();}}}}
}

============

先启动服务端，在启动客户端，在服务端控制台看打印结果为：

你好

在启动客户端，结果为（因为服务端用来while(true)）：

你好

你好