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

/**
 * HttpServer is a simple web server. It supports only the GET method and only
 * HTML, text, GIF, and JPEG files.
 */
public class HttpServer {

   private static int DEFAULT_PORT = 80;
   private int        serverPort;
   
   public static void main(String[] args) {
      int port = DEFAULT_PORT;

      // Get command-lines arguments. If command-line arg "port" cannot be
      // converted to an integer, print a usage message and exit.

      if (args.length >= 1) {
         try {
            port = Integer.parseInt(args[0]);

         } catch(NumberFormatException ex) {
            System.out.println("Usage: HttpServer [port]");
            System.exit(0);
         }
      }

      (new HttpServer(port)).go();
   }

   /**
    * Constructs a new HttpServer that listens on the default port.
    */
   public HttpServer() {
      this(DEFAULT_PORT);
   }

   /**
    * Constructs a new HttpServer that listens on the specified port.
    */
   public HttpServer(int port) {
      super();
      this.serverPort = port;
   }

   /**
    * Starts the server.
    */
   public void go() {
      ServerSocket       httpSocket;
      Socket             clientSocket;
      HttpRequestThread  requestThread;

      try {
         httpSocket = new ServerSocket(serverPort);
         System.out.println("HttpServer running on port " + serverPort + ".");

         try {
            while (true) {
               System.out.println("Waiting ...");

               // Accept any client connection.

               clientSocket = httpSocket.accept();
               System.out.println("Request received.");

               // Start a thread to service the client request.

               requestThread = new HttpRequestThread(clientSocket);
               requestThread.start();
               System.out.println("Request thread started.");
            }
         } finally {
            httpSocket.close();
         }
         
      } catch(Exception ex) {
         System.out.println(ex.toString());
      }

      System.exit(0);
   }

}