java.Network.EchoProgram(1:1)

package step4;

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

public class EchoServer {

	public void go() throws IOException {
		// 서버에 연결하여 통신하기 위해 Socket을 생성
		ServerSocket serverSocket = null;
		PrintWriter pw = null;
		BufferedReader br = null;
		String clientIp = null;
		Socket socket = null;
		try {
			// socket 연결
			serverSocket = new ServerSocket(7777);
			System.out.println("**EchoServer 실행**");
			// accept();
			socket = serverSocket.accept();
			// client IP
			clientIp = socket.getInetAddress().toString();

			// stream 생성
			br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			pw = new PrintWriter(socket.getOutputStream(), true);// true : auto flush(쓰자마자 바로 쏨)

			while (true) {
				String message = br.readLine();
				if (message.equals("종료종료")) {
					System.out.println("Echo프로그램을 종료합니다.");
					break;
				}
				System.out.println(clientIp + "  :  " + message);
				pw.println(message);
				System.out.println(message + "를 " + clientIp + "로 보냄");

			}
		} finally {
			if (socket != null) {
				socket.close();
			}
			if (pw != null) {
				pw.close();
			}
			if (br != null) {
				br.close();
			}
		}
	}

	public static void main(String[] args) {
		try {
			new EchoServer().go();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

package step4;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

import step1.IP;

public class EchoClient {
	public void go() throws IOException {
		// 서버에 연결하여 통신하기 위해 Socket을 생성
		Socket socket = null;
		PrintWriter pw = null;
		Scanner scanner = null;
		BufferedReader br = null;
		try {
			scanner = new Scanner(System.in);
			socket = new Socket(IP.LOCAL, 7777);
			System.out.println("**EchoServer접속완료**");
			// in/out put stream 생성
			pw = new PrintWriter(socket.getOutputStream(), true);
			br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			while (true) {
				// 메세지 입력 받음
				System.out.print("입력하거라: ");
				String message = scanner.nextLine();
				// 서버에 메세지 보냄
				pw.println(message);
				if (message.equals("종료종료")) {
					System.out.println("Echo프로그램을 종료합니다.");
					break;
				}
				System.out.println(message + "를 서버에게 보냄");
				// 서버에게 돌려 받은 에코 메세지를 출력
				System.out.println(br.readLine() + "from server");

			}
		} finally {
			if (socket != null) {
				socket.close();
			}
			if (pw != null) {
				pw.close();
			}
			if (scanner != null) {
				scanner.close();
			}
			if (br != null) {
				br.close();
			}
		}

	}

	public static void main(String[] args) {
		try {
			new EchoClient().go();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

package step1;

public interface IP {
	//public static final 상수 : IP.LOCAL 로 접근 
	//나의 IP 
	String LOCAL="127.0.0.1";
	//서버의 IP 
	String INST="221.150.136.4";
}