Simple http web server 2

[JontyMC]

Hi,

I need code for a very basic http web server. Can anyone help me out or point me in the right direction?

Thanks

 

[sedj]

You will need to use the ServerSocket class and the Socket class :

http://java.sun.com/j2se/1.4.2/docs/api/java/net/ServerSocket.html

http://java.sun.com/j2se/1.4.2/docs/api/java/net/Socket.html

You basically create a new ServerSocket on the port you wish to listen on, and then sit in a loop calling accept() on each incoming request to create a Socket object. Once you have this you can access the incoming requests IO streams.

 

[JontyMC]

Thanks for the reply. Could you possible elaborate a bit further, plus how do I handle http requests?

 

[sedj]

ServerSocket and Socket are TCP/IP sockets. HTTP goes over these protocols, so you would have to handle it yourself. For example, an HTTP request over TCP/IP would look something like :

HTTP 1.0 GET /pages/aPage.html

so you would use a StringTokenizer to work out the resource requsted and to get the HTTP method etc.

So :

ServerSocket ss = new ServerSocket(80);
while (true) {
  Socket s = ss.accept(); 
  InputStream is = s.getInputStream();
  OutputStream os = s.getOutputStream();
}

This is just a hint as to what you would need to do. In reality this blocks on each incoming request, and ideally you would want an inner class that extends Thread to handle each request and so each Socket created by the accept() method.

 

[hologram]

The following is taken from the book "Inside Servlets" by Dustin R. Callaway :

"The following code implements a generic HTTP server. This simple server accepts GET and HEAD requests from the client and returns HTML files and image data. Adding a "-v" command-line parameter will enable verbose mode which displays all connections in the HTTP server's console window."

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

/**
 * Java HTTP Server
 *
 * This simple HTTP server supports GET and HEAD requests.
 *
 * @author Dustin R. Callaway
 * @version 1.0, 02/09/98
 */
public class HttpServer implements Runnable
{
  //static constants
  //HttpServer root is the current directory
  static final File WEB_ROOT = new File(".");
  static final String DEFAULT_FILE = "index.html";
  static final int PORT = 8080; //default port

  //static variables
  static boolean verbose=false;

  //instance variables
  Socket connect;


  //constructor
  public HttpServer(Socket connect)
  {
    this.connect = connect;
  }


  /**
   * main method creates a new HttpServer instance for each
   * request and starts it running in a separate thread
   */
  public static void main(String[] args)
  {
    ServerSocket serverConnect=null;

    if (args.length > 0)
    {
      if (args[0].equals("-v") || args[0].equals("-verbose"))
      {
        verbose = true; //print status to standard out
      }
      else if (args[0].equals("-?") || args[0].equals("-help"))
      {
        //print instructions to standard out
        String instructions =
          "usage: java HttpServer [-options]\n\n" +
          "where options include:\n" +
          "    -? -help\t print out this message\n" +
          "    -v -verbose\t turn on verbose mode";

        System.out.println(instructions);
        return;
      }
    }

    try
    {
      serverConnect = new ServerSocket(PORT); //listen on port
      System.out.println("\nListening for connections on port "
        + PORT + "...\n");
      while (true) //listen until user halts execution
      {
        HttpServer server = new HttpServer(
          serverConnect.accept()); //instantiate HttpServer
        if (verbose)
        {
          System.out.println("Connection opened. (" +
            new Date() + ")");
        }
        //create new thread
        Thread threadRunner = new Thread(server);
        threadRunner.start(); //start thread
      }
    }
    catch (IOException e)
    {
      System.err.println("Server error: " + e);
    }
  }


  /**
   * run method services each request in a separate thread
   */
  public void run()
  {
    try
    {
      //get character input stream from client
      BufferedReader in = new BufferedReader(new
        InputStreamReader(connect.getInputStream()));
      //get character output stream to client (for headers)
      PrintWriter out = new PrintWriter(
        connect.getOutputStream());
      //get binary output stream to client (for requested data)
      BufferedOutputStream dataOut = new BufferedOutputStream(
        connect.getOutputStream());

      //get first line of request from client
      String input = in.readLine();
      //create StringTokenizer to parse request
      StringTokenizer parse = new StringTokenizer(input);
      //parse out method
      String method = parse.nextToken().toUpperCase();
      //parse out file requested
      String fileRequested = parse.nextToken().toLowerCase();

      //methods other than GET and HEAD are not implemented
      if (!method.equals("GET") && !method.equals("HEAD"))
      {
        if (verbose)
        {
          System.out.println("501 Not Implemented: " + method +
            " method.");
        }

        //send Not Implemented message to client
        out.println("HTTP/1.0 501 Not Implemented");
        out.println("Server: HttpServer 1.0");
        out.println("Date: " + new Date());
        out.println("Content-Type: text/html");
        out.println(); //blank line between headers and content
        out.println("<HTML>");
        out.println("<HEAD><TITLE>Not Implemented</TITLE>" +
          "</HEAD>");
        out.println("<BODY>");
        out.println("<H2>501 Not Implemented: " + method +
          " method.</H2>");
        out.println("</BODY></HTML>");
        out.flush();
        out.close(); //close output stream
        connect.close(); //close socket connection

        if (verbose)
        {
          System.out.println("Connection closed.\n");
        }

        return;
      }

      //If we get to here, request method is GET or HEAD

      if (fileRequested.endsWith("/"))
      {
        //append default file name to request
        fileRequested += DEFAULT_FILE;
      }

      try
      {
        //create file object
        File file = new File(WEB_ROOT, fileRequested);
        //get length of file
        int fileLength = (int)file.length();

        //get the file's MIME content type
        String content = getContentType(fileRequested);

        //generate HTTP headers
        out.println("HTTP/1.0 200 OK");
        out.println("Server: HttpServer 1.0");
        out.println("Date: " + new Date());
        out.println("Content-type: " + content);
        out.println("Content-length: " + file.length());
        out.println(); //blank line between headers and content
        out.flush(); //flush character output stream buffer

        //if request is a GET, send the file content
        if (method.equals("GET"))
        {
          //open input stream from file
          FileInputStream fileIn = new FileInputStream(file);
          //create byte array to store file data
          byte[] fileData = new byte[fileLength];
          //read file into byte array
          fileIn.read(fileData);
          fileIn.close(); //close file input stream

          dataOut.write(fileData,0,fileLength); //write file
          dataOut.flush(); //flush binary output stream buffer
        }

        if (verbose)
        {
          System.out.println("File " + fileRequested +
            " of type " + content + " returned.");
        }

        out.close(); //close character output stream
        dataOut.close(); //close binary output stream
        connect.close(); //close socket connection
        if (verbose)
        {
          System.out.println("Connection closed.\n");
        }
      }
      catch (IOException e)
      {
        //inform client file doesn't exist
        fileNotFound(out, fileRequested);

        out.close();
        connect.close();
        if (verbose)
        {
          System.out.println("Connection closed.\n");
        }
      }
    }
    catch (IOException e)
    {
      System.err.println("Server Error: " + e);
    }
  }


  /**
   * fileNotFound informs client that requested file does not
   * exist.
   *
   * @param out Client output stream
   * @param file File requested by client
   */
  private void fileNotFound(PrintWriter out, String file)
    throws IOException
  {
    out.println("HTTP/1.0 404 File Not Found");
    out.println("Server: HttpServer 1.0");
    out.println("Date: " + new Date());
    out.println("Content-Type: text/html");
    out.println();
    out.println("<HTML>");
    out.println("<HEAD><TITLE>File Not Found</TITLE>" +
      "</HEAD>");
    out.println("<BODY>");
    out.println("<H2>404 File Not Found: " + file + "</H2>");
    out.println("</BODY>");
    out.println("</HTML>");
    if (verbose)
    {
      System.out.println("404 File Not Found: " + file);
    }
  }


  /**
   * getContentType returns the proper MIME content type
   * according to the requested file's extension
   *
   * @param fileRequested File requested by client
   */
  private String getContentType(String fileRequested)
  {
    if (fileRequested.endsWith(".htm") ||
      fileRequested.endsWith(".html"))
    {
      return "text/html";
    }
    else if (fileRequested.endsWith(".gif"))
    {
      return "image/gif";
    }
    else if (fileRequested.endsWith(".jpg") ||
      fileRequested.endsWith(".jpeg"))
    {
      return "image/jpeg";
    }
    else if (fileRequested.endsWith(".class") ||
      fileRequested.endsWith(".jar"))
    {
      return "applicaton/octet-stream";
    }
    else
    {
      return "text/plain";
    }
  }
}