Tcp协议创建一个客户端和服务端（提供聊天）

//客户端
package tcpdemo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class StringSendDemo {

	public static void main(String[] args) throws UnknownHostException, IOException {
		// TODO Auto-generated method stub
		Socket s = new Socket("192.168.2.143",10003);
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter out = new PrintWriter(s.getOutputStream(),true);
		BufferedReader bfrin =  new BufferedReader(new InputStreamReader(s.getInputStream()));
		
		String line = null;
		
		byte buf[] = new byte[1024];
		while((line = br.readLine()) != null)
		{
			if(line.equals("over"))break;
			out.println(line);
			
			String string = bfrin.readLine();
			System.out.println(string);
		}
		
		s.close();
		br.close();
		bfrin.close();
		out.close();

	}

}

//服务端

package tcpdemo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class StringServerDemo {

	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		ServerSocket ss = new ServerSocket(10003);
		
		Socket s = ss.accept();
		BufferedReader brin = new BufferedReader(new InputStreamReader(s.getInputStream()));
		byte buf[] = new byte[1024];
		
		String line = null;
		PrintWriter os = new PrintWriter(s.getOutputStream(),true);
		while((line = brin.readLine()) != null)
		{
			System.out.println(line);
			os.println(line.toUpperCase());
		}
		
		ss.close();
		s.close();
		brin.close();
		os.close();
	}

}