jwebserver.java

JAMPACK Grid programming

/** 
 *
 * Program         : JWebserver.java 
 *
 * Author          : Vijayakrishnan Menon
 *
 * Date            : 20th Dec 2005
 *
 *Organization    : Centre for Excellence in 
 *						Computational Engineering and Networking (CEN),
 *                   		Amrita Viswa Vidyapeetham
 */ 

package JAMPack;

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

/** The server serves files only in the current directory and subdirectories.
  * It does not support CGI, cookies, authentication, keepalive, etc.
  * Client requests are logged to standard output.
  *
  * Webserver accepts HTTP GET requests that begin with: 
  *  	GET /filename.html
  *
  * If the file exists, it responds with:    
  * 	HTTP/1.0 200 OK\r\n	Content-Type: text/html\r\n	\r\n
  * 
  * (contents of filename.html)
  * where \r\n is a carriage return and line feed.  The content type depends
  * on the filename extension as follows:
  * 	.html   text/html
  * 	.htm    text/html
  * 	.gif    image/gif
  * 	.jpeg   image/jpeg
  * 	.jpg    image/jpeg
  * 	.class  application/octet-stream
  * 	.text/plain  (all other extensions)
  *
  * The server closes the connection after returning a file.  Keepalive
  * (the default in HTTP/1.1) is not implemented.
  * If the file does not exist or the request is not understood, the server
  *
  * sends an HTTP "404 Not Found" error message back to the client.
  *
  * If the client requests a directory without a trailing "/",
  * then the client is redirected to append it with an "HTTP 301 Moved
  *
  * Permanently" response.  If the trailing slash is present, the server
  * returns the file index.html if it exists.
  *
  * To prevent access outside the directory tree where the server was started,
  * file names containing "..", "|", or ":" are rejected.
  **/
  
public class JWebserver {
	private static ServerSocket serverSocket;
  	      
    public static void startServer() throws IOException {
    	serverSocket=new ServerSocket(JEnvironment.WEB_PORT);  
	    while (true) {
		    try {
			    Socket s = serverSocket.accept();  // Wait for a client to connect
			    new ClientHandler(s);  // Handle the client in a separate thread
		    }
		    catch (Exception x) { 	System.out.println(x);    }
	    }
	}
}

/** A ClientHandler reads an HTTP request and responds */
class ClientHandler extends Thread {
  private Socket socket;  

  /** Start the thread in the constructor */
  public ClientHandler(Socket s) {
    socket=s;
    start();
  }

  /** Read the HTTP request, respond, and close the connection*/
  public void run() {
    try {     
      BufferedReader in=new BufferedReader(new InputStreamReader(
        socket.getInputStream()));
      PrintStream out=new PrintStream(new BufferedOutputStream(
        socket.getOutputStream()));

      // Read filename from first input line "GET /filename.html ..."
      // or if not in this format, treat as a file not found.
      String s=in.readLine();
      System.out.println(s);  // Log the request
 
      // Attempt to serve the file.  Catch FileNotFoundException and
      // return an HTTP error "404 Not Found".  Treat invalid requests
      // the same way.
      String filename="";
      StringTokenizer st=new StringTokenizer(s);
      try {

        // Parse the filename from the GET command
        if (st.hasMoreElements() && st.nextToken().equalsIgnoreCase("GET")
            && st.hasMoreElements())
          filename=st.nextToken();
        else
          throw new FileNotFoundException();  // Bad request

        // Append trailing "/" with "index.html"
        if (filename.endsWith("/"))
          filename+="index.html";

        // Remove leading / from filename
        while (filename.indexOf("/")==0)
          filename=filename.substring(1);

        // Replace "/" with "\" in path for PC-based servers
        filename=filename.replace('/', File.separator.charAt(0));

        // Check for illegal characters to prevent access to superdirectories
        if (filename.indexOf("..")>=0 || filename.indexOf(':')>=0
            || filename.indexOf('|')>=0)
          throw new FileNotFoundException();

        // If a directory is requested and the trailing / is missing,
        // send the client an HTTP request to append it.  (This is
        // necessary for relative links to work correctly in the client).
        if (new File(filename).isDirectory()) {
          filename=filename.replace('\\', '/');
          out.print("HTTP/1.0 301 Moved Permanently\r\n"+
            "Location: /"+filename+"/\r\n\r\n");
          out.close();
          return;
        }

        // Open the file (may throw FileNotFoundException)
        InputStream f=new FileInputStream(filename);

        // Determine the MIME type and print HTTP header
        String mimeType="text/plain";
        if (filename.endsWith(".html") || filename.endsWith(".htm"))
          mimeType="text/html";
        else if (filename.endsWith(".jpg") || filename.endsWith(".jpeg"))
          mimeType="image/jpeg";
        else if (filename.endsWith(".gif"))
          mimeType="image/gif";
        else if (filename.endsWith(".class"))
          mimeType="application/octet-stream";
        out.print("HTTP/1.0 200 OK\r\n"+"Content-type: "+mimeType+"\r\n\r\n");

        // Send file contents to client, then close the connection
        byte[] a=new byte[4096];
        int n;
        while ((n=f.read(a))>0)
          out.write(a, 0, n);
        out.close();
      }
      catch (FileNotFoundException x) {
        out.println("HTTP/1.0 404 Not Found\r\n"+
            "Content-type: text/html\r\n\r\n"+
                "<html><head></head><body>"+filename+" not found</body></html>\n");
        out.close();
      }
    }
    catch (IOException x) {
      System.out.println(x);
    }
  }
}