客户端从键盘输入信息，发到服务端，服务端收到信息后，转成大写返回给客户端。

Server

package com.hbsi.net;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer {

/**
  * @param args
  */
public static void main(String[] args) throws Exception{
  ServerSocket ss=new ServerSocket(3366);
  Socket s=ss.accept();
  System.out.println(s.getInetAddress().getHostAddress()+"......connection");
  InputStream in = s.getInputStream();
  BufferedReader brin=new BufferedReader(new InputStreamReader(in));
  BufferedWriter bwout=new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
 
  String line=null;
  while((line=brin.readLine())!=null){
   if(line.equals("over"))
    break;
   System.out.println("Client:"+line);
  
   bwout.write(line.toUpperCase());
   bwout.newLine();
   bwout.flush();
  }
  s.close();
  ss.close();
}

}

Client

package com.hbsi.net;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;

public class TCPClient {

/**
  * @param args
  */
public static void main(String[] args) throws Exception {
  Socket s = new Socket("192.168.49.2", 3366);
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  BufferedWriter bwout = new BufferedWriter(new OutputStreamWriter(s
    .getOutputStream()));
  BufferedReader brin = new BufferedReader(new InputStreamReader(s
    .getInputStream()));
  String line = null;
  while ((line = br.readLine()) != null) {
   if(line.equals("over"))
    break;
   bwout.write(line);
   bwout.newLine();
   bwout.flush();
   String str = brin.readLine();
   System.out.println("server:" + str);

  }
  br.close();
  s.close();
}

}