/**
 * This program is a very simple Web server.  When it receives a HTTP request
 * it sends the request back as the reply.  This can be of interest when
 * you want to see just what a Web client is requesting, or what data is
 * being sent when a form is submitted, for example.
 **/

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

public class HttpMirror {
  public static void main(String args[]) {
    try {
      // Get the port to listen on
      int port = Integer.parseInt(args[0]);

      // Create a ServerSocket to listen on that port.
      ServerSocket ss = new ServerSocket(port);

      // Now enter an infinite loop, waiting for connections and handling them.

      for(;;) {
        // Wait for a client to connect.  The method will block, and when it
        // returns the socket will be already connected to the client

        Socket client = ss.accept();

        // Get input and output streams to talk to the client from the socket

        BufferedReader in = 
          new BufferedReader(new InputStreamReader(client.getInputStream()));
        PrintWriter out =
          new PrintWriter(new OutputStreamWriter(client.getOutputStream()));

        // Start sending our reply, using the HTTP 1.0 protocol

        out.println("HTTP/1.0 200 ");              // Version & status code
        out.println("Content-Type: text/plain");   // The type of data we send
        out.println();                             // End of response headers
        out.flush();

        // Now, read the HTTP request from the client, and send it right
        // back to the client as part of the body of our response.
        // The client doesn't disconnect, so we never get an EOF.
        // It does sends an empty line at the end of the headers, though.  
        // So when we see the empty line, we stop reading.  This means we 
        // don't mirror the contents of POST requests, for example.

        String line;
        while((line = in.readLine()) != null) {
          if (line.length() == 0) break;
          out.println(line);
        }

        // Close the streams and socket, breaking the connection to the client
        out.close();
        in.close();
        client.close();
      } // Loop again, waiting for the next connection
    }
    // If anything goes wrong, print an error message
    catch (Exception e) {
      System.err.println(e);
      System.err.println("Usage: java HttpMirror <port>");
    }
  }
}