Java/Network Protocol/Web Server

A simple HTTP server that displays information about all accessible printers on the network

  
 
/*
 * Copyright (c) 2004 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 3nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose,
 * including teaching and use in open-source projects.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book, 
 * please visit http://www.davidflanagan.ru/javaexamples3.
 */
//package je3.nio;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.util.Iterator;
import java.util.Set;
import javax.print.PrintService;
import javax.print.PrintServiceLookup;
import javax.print.attribute.Attribute;
/**
 * PrintServiceWebInterface: A simple HTTP server that displays information
 * about all accessible printers on the network.
 */
public class PrintServiceWebInterface {
  public static void main(String[] args) throws IOException {
    // Get the character encoders and decoders we"ll need
    Charset charset = Charset.forName("ISO-8859-1");
    CharsetEncoder encoder = charset.newEncoder();
    // The HTTP headers we send back to the client are fixed
    String headers = "HTTP/1.1 200 OK\r\n" + "Content-type: text/html\r\n"
        + "Connection: close\r\n" + "\r\n";
    // We"ll use two buffers in our response. One holds the fixed
    // headers, and the other holds the variable body of the response.
    ByteBuffer[] buffers = new ByteBuffer[2];
    buffers[0] = encoder.encode(CharBuffer.wrap(headers));
    ByteBuffer body = ByteBuffer.allocateDirect(16 * 1024);
    buffers[1] = body;
    // Find all available PrintService objects to describe
    PrintService[] services = PrintServiceLookup.lookupPrintServices(null, null);
    // All of the channels we use in this code will be in non-blocking
    // mode. So we create a Selector object that will block while
    // monitoring all of the channels and will only stop blocking when
    // one or more of the channels is ready for I/O of some sort.
    Selector selector = Selector.open();
    // Create a new ServerSocketChannel, and bind it to port 8000.
    // Note that we have to do this using the underlying ServerSocket.
    ServerSocketChannel server = ServerSocketChannel.open();
    server.socket().bind(new java.net.InetSocketAddress(8000));
    // Put the ServerSocketChannel into non-blocking mode
    server.configureBlocking(false);
    // Now register the channel with the Selector. The SelectionKey
    // represents the registration of this channel with this Selector.
    SelectionKey serverkey = server.register(selector, SelectionKey.OP_ACCEPT);
    for (;;) { // The main server loop. The server runs forever.
      // This call blocks until there is activity on one of the
      // registered channels. This is the key method in non-blocking I/O.
      selector.select();
      // Get a java.util.Set containing the SelectionKey objects for
      // all channels that are ready for I/O.
      Set keys = selector.selectedKeys();
      // Use a java.util.Iterator to loop through the selected keys
      for (Iterator i = keys.iterator(); i.hasNext();) {
        // Get the next SelectionKey in the set, and then remove it
        // from the set. It must be removed explicitly, or it will
        // be returned again by the next call to select().
        SelectionKey key = (SelectionKey) i.next();
        i.remove();
        // Check whether this key is the SelectionKey we got when
        // we registered the ServerSocketChannel.
        if (key == serverkey) {
          // Activity on the ServerSocketChannel means a client
          // is trying to connect to the server.
          if (key.isAcceptable()) {
            // Accept the client connection, and obtain a
            // SocketChannel to communicate with the client.
            SocketChannel client = server.accept();
            // Make sure we actually got a connection
            if (client == null)
              continue;
            // Put the client channel in non-blocking mode.
            client.configureBlocking(false);
            // Now register the client channel with the Selector,
            // specifying that we"d like to know when there is
            // data ready to read on the channel.
            SelectionKey clientkey = client.register(selector, SelectionKey.OP_READ);
          }
        } else {
          // If the key we got from the Set of keys is not the
          // ServerSocketChannel key, then it must be a key
          // representing one of the client connections.
          // Get the channel from the key.
          SocketChannel client = (SocketChannel) key.channel();
          // If we got here, it should mean that there is data to
          // be read from the channel, but we double-check here.
          if (!key.isReadable())
            continue;
          // Now read bytes from the client. We assume that
          // we get all the client"s bytes in one read operation
          client.read(body);
          // The data we read should be some kind of HTTP GET
          // request. We don"t bother checking it however since
          // there is only one page of data we know how to return.
          body.clear();
          // Build an HTML document as our reponse.
          // The body of the document contains PrintService details
          StringBuffer response = new StringBuffer();
          response.append("<html><head><title>Printer Status</title></head>"
              + "<body><h1>Printer Status</h1>");
          for (int s = 0; s < services.length; s++) {
            PrintService service = services[s];
            response.append("<h2>").append(service.getName()).append("</h2><table>");
            Attribute[] attrs = service.getAttributes().toArray();
            for (int a = 0; a < attrs.length; a++) {
              Attribute attr = attrs[a];
              response.append("<tr><td>").append(attr.getName()).append("</td><td>").append(attr)
                  .append("</tr>");
            }
            response.append("</table>");
          }
          response.append("</body></html>\r\n");
          // Encode the response into the body ByteBuffer
          encoder.reset();
          encoder.encode(CharBuffer.wrap(response), body, true);
          encoder.flush(body);
          body.flip(); // Prepare the body buffer to be drained
          // While there are bytes left to write
          while (body.hasRemaining()) {
            // Write both header and body buffers
            client.write(buffers);
          }
          buffers[0].flip(); // Prepare header buffer for next write
          body.clear(); // Prepare body buffer for next read
          // Once we"ve sent our response, we have no more interest
          // in the client channel or its SelectionKey
          client.close(); // Close the channel.
          key.cancel(); // Tell Selector to stop monitoring it.
        }
      }
    }
  }
}

A simple, tiny, nicely embeddable HTTP 1.0 server in Java

   
/*
 "Copyright (C) 2001,2005 by Jarno Elonen <elonen@iki.fi>\n"+
 "\n"+
 "Redistribution and use in source and binary forms, with or without\n"+
 "modification, are permitted provided that the following conditions\n"+
 "are met:\n"+
 "\n"+
 "Redistributions of source code must retain the above copyright notice,\n"+
 "this list of conditions and the following disclaimer. Redistributions in\n"+
 "binary form must reproduce the above copyright notice, this list of\n"+
 "conditions and the following disclaimer in the documentation and/or other\n"+
 "materials provided with the distribution. The name of the author may not\n"+
 "be used to endorse or promote products derived from this software without\n"+
 "specific prior written permission. \n"+
 " \n"+
 "THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS"" AND ANY EXPRESS OR\n"+
 "IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES\n"+
 "OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.\n"+
 "IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,\n"+
 "INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT\n"+
 "NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,\n"+
 "DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY\n"+
 "THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT\n"+
 "(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE\n"+
 "OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.";
 */
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.URLEncoder;
import java.util.Date;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Locale;
import java.util.Properties;
import java.util.StringTokenizer;
import java.util.TimeZone;
/**
 * A simple, tiny, nicely embeddable HTTP 1.0 server in Java
 * 
 * <p>
 * NanoHTTPD version 1.1, Copyright &copy; 2001,2005-2007 Jarno Elonen
 * (elonen@iki.fi, http://iki.fi/elonen/)
 * 
 * <p>
 * <b>Features + limitations: </b>
 * <ul>
 * 
 * <li> Only one Java file </li>
 * <li> Java 1.1 compatible </li>
 * <li> Released as open source, Modified BSD licence </li>
 * <li> No fixed config files, logging, authorization etc. (Implement yourself
 * if you need them.) </li>
 * <li> Supports parameter parsing of GET and POST methods </li>
 * <li> Supports both dynamic content and file serving </li>
 * <li> Never caches anything </li>
 * <li> Doesn"t limit bandwidth, request time or simultaneous connections </li>
 * <li> Default code serves files and shows all HTTP parameters and headers</li>
 * <li> File server supports directory listing, index.html and index.htm </li>
 * <li> File server does the 301 redirection trick for directories without "/"</li>
 * <li> File server supports simple skipping for files (continue download) </li>
 * <li> File server uses current directory as a web root </li>
 * <li> File server serves also very long files without memory overhead </li>
 * <li> Contains a built-in list of most common mime types </li>
 * <li> All header names are converted lowercase so they don"t vary between
 * browsers/clients </li>
 * 
 * </ul>
 * 
 * <p>
 * <b>Ways to use: </b>
 * <ul>
 * 
 * <li> Run as a standalone app, serves files from current directory and shows
 * requests</li>
 * <li> Subclass serve() and embed to your own program </li>
 * <li> Call serveFile() from serve() with your own base directory </li>
 * 
 * </ul>
 * 
 * See the end of the source file for distribution license (Modified BSD
 * licence)
 */
public class NanoHTTPD {
  // 
  // API parts
  // 
  /**
   * Override this to customize the server.
   * <p>
   * 
   * (By default, this delegates to serveFile() and allows directory listing.)
   * 
   * @parm uri Percent-decoded URI without parameters, for example "/index.cgi"
   * @parm method "GET", "POST" etc.
   * @parm parms Parsed, percent decoded parameters from URI and, in case of
   *       POST, data.
   * @parm header Header entries, percent decoded
   * @return HTTP response, see class Response for details
   */
  public Response serve(String uri, String method, Properties header, Properties parms) {
    System.out.println(method + " "" + uri + "" ");
    Enumeration e = header.propertyNames();
    while (e.hasMoreElements()) {
      String value = (String) e.nextElement();
      System.out.println("  HDR: "" + value + "" = "" + header.getProperty(value) + """);
    }
    e = parms.propertyNames();
    while (e.hasMoreElements()) {
      String value = (String) e.nextElement();
      System.out.println("  PRM: "" + value + "" = "" + parms.getProperty(value) + """);
    }
    return serveFile(uri, header, new File("."), true);
  }
  /**
   * HTTP response. Return one of these from serve().
   */
  public class Response {
    /**
     * Default constructor: response = HTTP_OK, data = mime = "null"
     */
    public Response() {
      this.status = HTTP_OK;
    }
    /**
     * Basic constructor.
     */
    public Response(String status, String mimeType, InputStream data) {
      this.status = status;
      this.mimeType = mimeType;
      this.data = data;
    }
    /**
     * Convenience method that makes an InputStream out of given text.
     */
    public Response(String status, String mimeType, String txt) {
      this.status = status;
      this.mimeType = mimeType;
      this.data = new ByteArrayInputStream(txt.getBytes());
    }
    /**
     * Adds given line to the header.
     */
    public void addHeader(String name, String value) {
      header.put(name, value);
    }
    /**
     * HTTP status code after processing, e.g. "200 OK", HTTP_OK
     */
    public String status;
    /**
     * MIME type of content, e.g. "text/html"
     */
    public String mimeType;
    /**
     * Data of the response, may be null.
     */
    public InputStream data;
    /**
     * Headers for the HTTP response. Use addHeader() to add lines.
     */
    public Properties header = new Properties();
  }
  /**
   * Some HTTP response status codes
   */
  public static final String HTTP_OK = "200 OK", HTTP_REDIRECT = "301 Moved Permanently",
      HTTP_FORBIDDEN = "403 Forbidden", HTTP_NOTFOUND = "404 Not Found",
      HTTP_BADREQUEST = "400 Bad Request", HTTP_INTERNALERROR = "500 Internal Server Error",
      HTTP_NOTIMPLEMENTED = "501 Not Implemented";
  /**
   * Common mime types for dynamic content
   */
  public static final String MIME_PLAINTEXT = "text/plain", MIME_HTML = "text/html",
      MIME_DEFAULT_BINARY = "application/octet-stream";
  // 
  // Socket & server code
  // 
  /**
   * Starts a HTTP server to given port.
   * <p>
   * Throws an IOException if the socket is already in use
   */
  public NanoHTTPD(int port) throws IOException {
    myTcpPort = port;
    final ServerSocket ss = new ServerSocket(myTcpPort);
    Thread t = new Thread(new Runnable() {
      public void run() {
        try {
          while (true)
            new HTTPSession(ss.accept());
        } catch (IOException ioe) {
        }
      }
    });
    t.setDaemon(true);
    t.start();
  }
  /**
   * Starts as a standalone file server and waits for Enter.
   */
  public static void main(String[] args) {
    System.out.println("NanoHTTPD 1.1 (C) 2001,2005-2007 Jarno Elonen\n"
        + "(Command line options: [port] [--licence])\n");
    // Show licence if requested
    int lopt = -1;
    for (int i = 0; i < args.length; ++i)
      if (args[i].toLowerCase().endsWith("licence")) {
        lopt = i;
        System.out.println(LICENCE + "\n");
      }
    // Change port if requested
    int port = 80;
    if (args.length > 0 && lopt != 0)
      port = Integer.parseInt(args[0]);
    if (args.length > 1 && args[1].toLowerCase().endsWith("licence"))
      System.out.println(LICENCE + "\n");
    NanoHTTPD nh = null;
    try {
      nh = new NanoHTTPD(port);
    } catch (IOException ioe) {
      System.err.println("Couldn"t start server:\n" + ioe);
      System.exit(-1);
    }
    nh.myFileDir = new File("");
    System.out.println("Now serving files in port " + port + " from \""
        + new File("").getAbsolutePath() + "\"");
    System.out.println("Hit Enter to stop.\n");
    try {
      System.in.read();
    } catch (Throwable t) {
    }
    ;
  }
  /**
   * Handles one session, i.e. parses the HTTP request and returns the response.
   */
  private class HTTPSession implements Runnable {
    public HTTPSession(Socket s) {
      mySocket = s;
      Thread t = new Thread(this);
      t.setDaemon(true);
      t.start();
    }
    public void run() {
      try {
        InputStream is = mySocket.getInputStream();
        if (is == null)
          return;
        BufferedReader in = new BufferedReader(new InputStreamReader(is));
        // Read the request line
        StringTokenizer st = new StringTokenizer(in.readLine());
        if (!st.hasMoreTokens())
          sendError(HTTP_BADREQUEST, "BAD REQUEST: Syntax error. Usage: GET /example/file.html");
        String method = st.nextToken();
        if (!st.hasMoreTokens())
          sendError(HTTP_BADREQUEST, "BAD REQUEST: Missing URI. Usage: GET /example/file.html");
        String uri = decodePercent(st.nextToken());
        // Decode parameters from the URI
        Properties parms = new Properties();
        int qmi = uri.indexOf("?");
        if (qmi >= 0) {
          decodeParms(uri.substring(qmi + 1), parms);
          uri = decodePercent(uri.substring(0, qmi));
        }
        // If there"s another token, it"s protocol version,
        // followed by HTTP headers. Ignore version but parse headers.
        // NOTE: this now forces header names uppercase since they are
        // case insensitive and vary by client.
        Properties header = new Properties();
        if (st.hasMoreTokens()) {
          String line = in.readLine();
          while (line.trim().length() > 0) {
            int p = line.indexOf(":");
            header.put(line.substring(0, p).trim().toLowerCase(), line.substring(p + 1).trim());
            line = in.readLine();
          }
        }
        // If the method is POST, there may be parameters
        // in data section, too, read it:
        if (method.equalsIgnoreCase("POST")) {
          long size = 0x7FFFFFFFFFFFFFFFl;
          String contentLength = header.getProperty("content-length");
          if (contentLength != null) {
            try {
              size = Integer.parseInt(contentLength);
            } catch (NumberFormatException ex) {
            }
          }
          String postLine = "";
          char buf[] = new char[512];
          int read = in.read(buf);
          while (read >= 0 && size > 0 && !postLine.endsWith("\r\n")) {
            size -= read;
            postLine += String.valueOf(buf, 0, read);
            if (size > 0)
              read = in.read(buf);
          }
          postLine = postLine.trim();
          decodeParms(postLine, parms);
        }
        // Ok, now do the serve()
        Response r = serve(uri, method, header, parms);
        if (r == null)
          sendError(HTTP_INTERNALERROR, "SERVER INTERNAL ERROR: Serve() returned a null response.");
        else
          sendResponse(r.status, r.mimeType, r.header, r.data);
        in.close();
      } catch (IOException ioe) {
        try {
          sendError(HTTP_INTERNALERROR, "SERVER INTERNAL ERROR: IOException: " + ioe.getMessage());
        } catch (Throwable t) {
        }
      } catch (InterruptedException ie) {
        // Thrown by sendError, ignore and exit the thread.
      }
    }
    /**
     * Decodes the percent encoding scheme. <br/> For example:
     * "an+example%20string" -> "an example string"
     */
    private String decodePercent(String str) throws InterruptedException {
      try {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < str.length(); i++) {
          char c = str.charAt(i);
          switch (c) {
          case "+":
            sb.append(" ");
            break;
          case "%":
            sb.append((char) Integer.parseInt(str.substring(i + 1, i + 3), 16));
            i += 2;
            break;
          default:
            sb.append(c);
            break;
          }
        }
        return new String(sb.toString().getBytes());
      } catch (Exception e) {
        sendError(HTTP_BADREQUEST, "BAD REQUEST: Bad percent-encoding.");
        return null;
      }
    }
    /**
     * Decodes parameters in percent-encoded URI-format ( e.g.
     * "name=Jack%20Daniels&pass=Single%20Malt" ) and adds them to given
     * Properties.
     */
    private void decodeParms(String parms, Properties p) throws InterruptedException {
      if (parms == null)
        return;
      StringTokenizer st = new StringTokenizer(parms, "&");
      while (st.hasMoreTokens()) {
        String e = st.nextToken();
        int sep = e.indexOf("=");
        if (sep >= 0)
          p.put(decodePercent(e.substring(0, sep)).trim(), decodePercent(e.substring(sep + 1)));
      }
    }
    /**
     * Returns an error message as a HTTP response and throws
     * InterruptedException to stop furhter request processing.
     */
    private void sendError(String status, String msg) throws InterruptedException {
      sendResponse(status, MIME_PLAINTEXT, null, new ByteArrayInputStream(msg.getBytes()));
      throw new InterruptedException();
    }
    /**
     * Sends given response to the socket.
     */
    private void sendResponse(String status, String mime, Properties header, InputStream data) {
      try {
        if (status == null)
          throw new Error("sendResponse(): Status can"t be null.");
        OutputStream out = mySocket.getOutputStream();
        PrintWriter pw = new PrintWriter(out);
        pw.print("HTTP/1.0 " + status + " \r\n");
        if (mime != null)
          pw.print("Content-Type: " + mime + "\r\n");
        if (header == null || header.getProperty("Date") == null)
          pw.print("Date: " + gmtFrmt.format(new Date()) + "\r\n");
        if (header != null) {
          Enumeration e = header.keys();
          while (e.hasMoreElements()) {
            String key = (String) e.nextElement();
            String value = header.getProperty(key);
            pw.print(key + ": " + value + "\r\n");
          }
        }
        pw.print("\r\n");
        pw.flush();
        if (data != null) {
          byte[] buff = new byte[2048];
          while (true) {
            int read = data.read(buff, 0, 2048);
            if (read <= 0)
              break;
            out.write(buff, 0, read);
          }
        }
        out.flush();
        out.close();
        if (data != null)
          data.close();
      } catch (IOException ioe) {
        // Couldn"t write? No can do.
        try {
          mySocket.close();
        } catch (Throwable t) {
        }
      }
    }
    private Socket mySocket;
  };
  /**
   * URL-encodes everything between "/"-characters. Encodes spaces as "%20"
   * instead of "+".
   */
  private String encodeUri(String uri) {
    String newUri = "";
    StringTokenizer st = new StringTokenizer(uri, "/ ", true);
    while (st.hasMoreTokens()) {
      String tok = st.nextToken();
      if (tok.equals("/"))
        newUri += "/";
      else if (tok.equals(" "))
        newUri += "%20";
      else {
        newUri += URLEncoder.encode(tok);
        // For Java 1.4 you"ll want to use this instead:
        // try { newUri += URLEncoder.encode( tok, "UTF-8" ); } catch (
        // UnsupportedEncodingException uee )
      }
    }
    return newUri;
  }
  private int myTcpPort;
  File myFileDir;
  // 
  // File server code
  // 
  /**
   * Serves file from homeDir and its" subdirectories (only). Uses only URI,
   * ignores all headers and HTTP parameters.
   */
  public Response serveFile(String uri, Properties header, File homeDir,
      boolean allowDirectoryListing) {
    // Make sure we won"t die of an exception later
    if (!homeDir.isDirectory())
      return new Response(HTTP_INTERNALERROR, MIME_PLAINTEXT,
          "INTERNAL ERRROR: serveFile(): given homeDir is not a directory.");
    // Remove URL arguments
    uri = uri.trim().replace(File.separatorChar, "/");
    if (uri.indexOf("?") >= 0)
      uri = uri.substring(0, uri.indexOf("?"));
    // Prohibit getting out of current directory
    if (uri.startsWith("..") || uri.endsWith("..") || uri.indexOf("../") >= 0)
      return new Response(HTTP_FORBIDDEN, MIME_PLAINTEXT,
          "FORBIDDEN: Won"t serve ../ for security reasons.");
    File f = new File(homeDir, uri);
    if (!f.exists())
      return new Response(HTTP_NOTFOUND, MIME_PLAINTEXT, "Error 404, file not found.");
    // List the directory, if necessary
    if (f.isDirectory()) {
      // Browsers get confused without "/" after the
      // directory, send a redirect.
      if (!uri.endsWith("/")) {
        uri += "/";
        Response r = new Response(HTTP_REDIRECT, MIME_HTML, "<html><body>Redirected: ";
          // Show file size
          if (curFile.isFile()) {
            long len = curFile.length();
            msg += " &nbsp;<font size=2>(";
            if (len < 1024)
              msg += curFile.length() + " bytes";
            else if (len < 1024 * 1024)
              msg += curFile.length() / 1024 + "." + (curFile.length() % 1024 / 10 % 100) + " KB";
            else
              msg += curFile.length() / (1024 * 1024) + "." + curFile.length() % (1024 * 1024) / 10
                  % 100 + " MB";
            msg += ")</font>";
          }
          msg += "<br/>";
          if (dir)
            msg += "</b>";
        }
        return new Response(HTTP_OK, MIME_HTML, msg);
      } else {
        return new Response(HTTP_FORBIDDEN, MIME_PLAINTEXT, "FORBIDDEN: No directory listing.");
      }
    }
    try {
      // Get MIME type from file name extension, if possible
      String mime = null;
      int dot = f.getCanonicalPath().lastIndexOf(".");
      if (dot >= 0)
        mime = (String) theMimeTypes.get(f.getCanonicalPath().substring(dot + 1).toLowerCase());
      if (mime == null)
        mime = MIME_DEFAULT_BINARY;
      // Support (simple) skipping:
      long startFrom = 0;
      String range = header.getProperty("Range");
      if (range != null) {
        if (range.startsWith("bytes=")) {
          range = range.substring("bytes=".length());
          int minus = range.indexOf("-");
          if (minus > 0)
            range = range.substring(0, minus);
          try {
            startFrom = Long.parseLong(range);
          } catch (NumberFormatException nfe) {
          }
        }
      }
      FileInputStream fis = new FileInputStream(f);
      fis.skip(startFrom);
      Response r = new Response(HTTP_OK, mime, fis);
      r.addHeader("Content-length", "" + (f.length() - startFrom));
      r.addHeader("Content-range", "" + startFrom + "-" + (f.length() - 1) + "/" + f.length());
      return r;
    } catch (IOException ioe) {
      return new Response(HTTP_FORBIDDEN, MIME_PLAINTEXT, "FORBIDDEN: Reading file failed.");
    }
  }
  /**
   * Hashtable mapping (String)FILENAME_EXTENSION -> (String)MIME_TYPE
   */
  private static Hashtable theMimeTypes = new Hashtable();
  static {
    StringTokenizer st = new StringTokenizer("htm    text/html " + "html   text/html "
        + "txt    text/plain " + "asc    text/plain " + "gif    image/gif " + "jpg    image/jpeg "
        + "jpeg   image/jpeg " + "png    image/png " + "mp3    audio/mpeg "
        + "m3u    audio/mpeg-url " + "pdf    application/pdf " + "doc    application/msword "
        + "ogg    application/x-ogg " + "zip    application/octet-stream "
        + "exe    application/octet-stream " + "class    application/octet-stream ");
    while (st.hasMoreTokens())
      theMimeTypes.put(st.nextToken(), st.nextToken());
  }
  /**
   * GMT date formatter
   */
  private static java.text.SimpleDateFormat gmtFrmt;
  static {
    gmtFrmt = new java.text.SimpleDateFormat("E, d MMM yyyy HH:mm:ss "GMT"", Locale.US);
    gmtFrmt.setTimeZone(TimeZone.getTimeZone("GMT"));
  }
  /**
   * The distribution licence
   */
  private static final String LICENCE = "Copyright (C) 2001,2005 by Jarno Elonen <elonen@iki.fi>\n"
      + "\n" + "Redistribution and use in source and binary forms, with or without\n"
      + "modification, are permitted provided that the following conditions\n" + "are met:\n"
      + "\n" + "Redistributions of source code must retain the above copyright notice,\n"
      + "this list of conditions and the following disclaimer. Redistributions in\n"
      + "binary form must reproduce the above copyright notice, this list of\n"
      + "conditions and the following disclaimer in the documentation and/or other\n"
      + "materials provided with the distribution. The name of the author may not\n"
      + "be used to endorse or promote products derived from this software without\n"
      + "specific prior written permission. \n" + " \n"
      + "THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS"" AND ANY EXPRESS OR\n"
      + "IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES\n"
      + "OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.\n"
      + "IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,\n"
      + "INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT\n"
      + "NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,\n"
      + "DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY\n"
      + "THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT\n"
      + "(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE\n"
      + "OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.";
}

A web server

   
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
public class MainClass {
  public static void main(String args[]) throws Exception {
    ServerSocket ss = new ServerSocket(80);
    while (true) {
      Socket s = ss.accept();
      PrintStream out = new PrintStream(s.getOutputStream());
      BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
      String info = null;
      while ((info = in.readLine()) != null) {
        System.out.println("now got " + info);
        if (info.equals(""))
          break;
      }
      out.println("HTTP/1.0 200 OK");
      out.println("MIME_version:1.0");
      out.println("Content_Type:text/html");
      String c = "<html> <head></head><body> <h1> hi</h1></Body></html>";
      out.println("Content_Length:" + c.length());
      out.println("");
      out.println(c);
      out.close();
      s.close();
      in.close();
    }
  }
}

Minimal HTTP Server by using com.sun.net.httpserver.HttpServer

   
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.util.List;
import java.util.Map;
import java.util.Set;
import com.sun.net.httpserver.Headers;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
public class MinimalHTTPServer {
  public static void main(String[] args) throws IOException {
    HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
    server.createContext("/echo", new Handler());
    server.start();
  }
}
class Handler implements HttpHandler {
  public void handle(HttpExchange xchg) throws IOException {
    Headers headers = xchg.getRequestHeaders();
    Set<Map.Entry<String, List<String>>> entries = headers.entrySet();
    StringBuffer response = new StringBuffer();
    for (Map.Entry<String, List<String>> entry : entries)
      response.append(entry.toString() + "\n");
    xchg.sendResponseHeaders(200, response.length());
    OutputStream os = xchg.getResponseBody();
    os.write(response.toString().getBytes());
    os.close();
  }
}

POSTing data to an HTTP server

  
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.URL;
import java.net.URLConnection;
public class Main {
  public static void main(String[] args) throws Exception {
    URL url = new URL("http://localhost:8080/postedresults.jsp");
    URLConnection conn = url.openConnection();
    conn.setDoInput(true);
    conn.setDoOutput(true);
    conn.setUseCaches(false);
    conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
    DataOutputStream out = new DataOutputStream(conn.getOutputStream());
    String content = "CONTENT=HELLO JSP !&ONEMORECONTENT =HELLO POST !";
    out.writeBytes(content);
    out.flush();
    out.close();
    DataInputStream in = new DataInputStream(conn.getInputStream());
    String str;
    while (null != ((str = in.readUTF()))) {
      System.out.println(str );
    }
    in.close();
  }
}