How hard is it to create a simple http server in java?

Question

how hard is it? where do i read on how to do it?

Answer 1

Here is a class I called EchoServer. It simply receives an HTTP request wraps some HTML around it and sends it back to your browser. It should give you an idea of a simple structure and the API's to look at.
Hope it helps.
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class EchoServer extends Object
     public static void main(String args[])
          throws IOException
          if ( args.length != 1)
               System.out.println("try: java EchoServer <port>");
               System.exit(-1);
          // Make sure port is numeric
          int port = -1;
          String portString = args[0];
          try
               port = Integer.parseInt(portString);
          catch(NumberFormatException nfe)
               System.out.println("port: " + portString + " is not a valid port number, try again");
               System.exit(-1);
          // Create server socket and loop forever handling each request as it is received
          ServerSocket server = null;
          try
               server = new ServerSocket( port );
               System.out.println( server );
               while ( true )
                    // this next line will wait until a client hits this port
                    Socket client = server.accept();
                    respond( client );
                    client.close();
          catch(Exception e)
               e.printStackTrace();
          finally
               if ( server != null )
                    server.close();
     public static void respond(Socket client)
          String request = getRequest( client);
          // Send request back wrapped in HTML
          OutputStream os = null;
          try
               os = client.getOutputStream();
               String response = "HTTP/1.0 200 Ok" + "\n"
                    + "Server: Echo Server" + "\n"
                    + "Content-type: text/html" + "\n"
                    + "\n"
                    + "<h2>The request you made was</h2>\n"
                    + "<pre>\n"
                    + "-------------------------------------\n"
                    + request
                    + "-------------------------------------\n"
                    + "</pre></html>\n";
               os.write(response.getBytes());
          catch(InterruptedIOException iioe)
          catch(IOException ioe)
               System.out.println(ioe.getMessage());
     private static String getRequest(Socket client)
String request = "";
byte[] iobuff = new byte[512];
int bytes;
          try
          // Wait 100 milliseconds before assuming the complete request has been received
          // Note: when this test wasn't here the server seemed to hang. If you find a better solution please let me know
          InputStream is = client.getInputStream();
          client.setSoTimeout(100);
while ( (bytes = is.read( iobuff )) != -1 )
String temp = new String( iobuff, 0, bytes );
request += temp;
//                    System.out.println(temp);
          catch(InterruptedIOException iioe)
               // this exception handles the socket timeout
          catch(IOException ioe)
               request = ioe.getMessage();
          return request;