[Java] Echo server & client

[참고] http://djeong.kunsan.ac.kr/teaching/08.02.fall.03.ComNet/Supplement-03-TCP%20Programming.pdf

Server

 
import java.net.Socket;
import java.net.ServerSocket;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
// import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.IOException;
 
public class EchoServer {
    
    private ServerSocket server;
    
    public EchoServer(int port)    throws IOException    {
        server = new ServerSocket(port);
    }
    
    public void service()    throws IOException    {
        System.out.println("EchoServer is ready.");
        Socket client = server.accept();
        InputStream is = client.getInputStream();
        OutputStream os = client.getOutputStream();
        BufferedReader in = new BufferedReader(new InputStreamReader(is));
        PrintWriter out = new PrintWriter(os, true);
        
        while(true)    {
            String msg = in.readLine();
            System.out.println(msg);
            
            if(msg.equals("bye"))    {
                break;
            }
            
            out.println(">> " + msg);
        }
    }
    
    public void close()    throws IOException {
        server.close();
    }
    
    public static void main(String args[])    {
        try    {
            EchoServer es = new EchoServer(1111);
            es.service();
            es.close();
        }    catch(Exception e)    {
            e.printStackTrace();
        }
    }    
}

Client

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
//import java.io.OutputStreamWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
 
public class EchoClient {
    private Socket socket;
    private EchoClient(String host, int port)    throws Exception    {
        socket = new Socket(host, port);
    }
    
    public void echo()    throws IOException    {
        OutputStream os = socket.getOutputStream();
        InputStream is = socket.getInputStream();
        BufferedReader in = new BufferedReader(new InputStreamReader(is));
        PrintWriter out = new PrintWriter(os, true);
        BufferedReader con = new BufferedReader(new InputStreamReader(System.in));
        
        while(true)    {
            String msg = con.readLine();
            out.println(msg);
            
            if(msg.equals("bye"))    break;
            
            System.out.println(in.readLine());
        }
    }
    
    public void close()    throws IOException    {
        socket.close();
    }
    
    public static void main(String args[])    {
        try    {
            EchoClient ec;
            
            System.out.println("Enter a message\n");
            
            if(args.length > 0)    ec = new EchoClient(args[0], 1111);
            else                 ec = new EchoClient("localhost", 1111);
            
            ec.echo();
            ec.close();
        }    catch(Exception e)    {
            e.printStackTrace();
        }
    }
}