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

public class TcpClient {

  public static final int DEFAULT_PORT = 6789;
  public static void usage() {
    System.out.println("Usage: java C [<port>]");
    System.exit(0);
  }
  
  public static void main(String[] args) {
    int port = DEFAULT_PORT;
    Socket s = null;
// parse the port specification
    if ((args.length != 0) && (args.length != 1)) usage();
    if (args.length == 0) port = DEFAULT_PORT;
    else {
      try {
        port = Integer.parseInt(args[0]);
      }
      catch(NumberFormatException e) {
        usage();
      }
    }
    try {
      BufferedReader reader;
      PrintWriter writer;
// create a socket to communicate to the specified host and port
      s = new Socket("localhost", port);
// create streams for reading and writing
      reader = new BufferedReader(new InputStreamReader(s.getInputStream()));
      writer = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
// tell the user that we've connected
      System.out.println("Connected to " + s.getInetAddress() +
        ":" + s.getPort());
      String line;
// write a line to the server
      writer.println("Hello, Server");
      writer.flush();
// read the response (a line) from the server
      line = reader.readLine();
// write the line to console
      System.out.println("Server says: " + line);
      reader.close();
      writer.close();
    }
    catch (IOException e) {
      System.err.println(e);
    }
// always be sure to close the socket
    finally {
      try {
        if (s != null) s.close();
      }
      catch (IOException e2) { }
    }
  }
}