import java.net.*;
import java.io.*;
import java.util.zip.*;

public class Echo {

    // java -client servername port
    // java -server port
    public static void main(String[] args) throws Throwable {
      
        if ("-client".equals(args[0])) {
            SocketIO sio = new SocketIO(new Socket(args[1],
                                        Integer.parseInt(args[2])));
            try {
                String ln;
                Console con = System.console();
                while((ln = sio.read()) != null) {
                    con.format("ECHO: %s", ln);
                    ln = con.readLine("%nMe  : ");
                    if(ln != null)
                        sio.write(ln);
                    if("exit".equals(ln))
                        break;
                }
	    } catch (IOException ioe) {
                ioe.printStackTrace();
            } finally {
                sio.close();
            } 
        } else if ("-server".equals(args[0])) {
            ServerSocket ss = new ServerSocket(Integer.parseInt(args[1]));
            while(true) {
                new SSThread(ss.accept()).start();
            }
        }
    }

    /**
     * Wraps a connected Socket object. It then can be used to read bytes
     * from/write bytes into the underlying socket streams.
     */
    private static class SocketIO {
        private Socket s;
        private OutputStream os;
        private InputStream is;
        SocketIO(Socket s) throws IOException {
	    this.s = s;
            this.os = s.getOutputStream();
            this.is = s.getInputStream();
	}
        byte[] bb = new byte[1024];
        String read() throws IOException {
            int n = is.read(bb);
            return new String(bb, 0, n);
        }
        void write(String ln) throws IOException {
            os.write(ln.getBytes());
            os.flush();
        }
        void close() {
            try {
                s.close();
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }
    }

    /**
     * A worker Thread that wraps a Socket object returned from ServerSocket.accept()
     * and echos every byte read from client.
     */
    static class SSThread extends Thread {
        private SocketIO sio;
        public SSThread(Socket s) throws IOException {
	    this.sio = new SocketIO(s);
        }
        public void run() {
            try {
	        sio.write("Welcome to ECHO!");
                String ln;
                while((ln = sio.read()) != null) {
                    sio.write(ln);
                    if("exit".equals(ln))
                        break;
		}
	    } catch (IOException ioe) {
                ioe.printStackTrace();
            } finally {
                sio.close();
            }
	}
    }
}