Servce.java

import java.net.*;
import java.io.*;

/**
 * Echo socket client
 */
public class Servce {
    public static void main(String[] args) {
        //open server socket on port 1234
        try {
            ServerSocket serverSocket = new ServerSocket(1234);
            while(!Thread.interrupted()) {
                //start a handle thread when accept
                new Thread(new Handler(serverSocket.accept())).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    static class Handler implements Runnable {

        final Socket socket;

        Handler(Socket socket) {
            this.socket = socket;
        }

        public void run() {
            try {
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(
                            socket.getInputStream(),
                            "UTF-8"));
                PrintWriter writer = new PrintWriter(
                        new OutputStreamWriter(
                            socket.getOutputStream(),
                            "UTF-8"),
                        true);

                String msg = null;
                while((msg = reader.readLine()) != null) {
                    if (null == msg || msg.isEmpty()) {
                        writer.println("exit");
                        break;
                    }
                    writer.println(process(msg));
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    socket.close();
                } catch (IOException e) {
                    //ignore
                }
            }
        }

        public String process(String in) {
            String out = in;
            return out;
        }
    }
}