Get hostname from request

Question

I'm running my application on Windows Server 2008 on an Intranet.

To login the application tries to get the hostname from the request to validate the user. However, sometimes the application returns the IP address instead of the name and some time later, without doing anything the application is able to resolve the name and everything works fine...

This is the code I'm using to get the hostname:

InetAddress inaHost = InetAddress.getByName(request.getRemoteAddr());
String hostname = inaHost.getHostName();
System.out.println("[[ Hostname = " + hostname + " ]]");

Is this because of the Intranet configuration (DNS!?), or is something wrong with my code, or witchcraft or something?

Answer 1

First try

System.out.println("Host = " + request.getServerName());
System.out.println("Port = " + request.getServerPort());

if doesnt work

hostName == null;
Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
{
  while (interfaces.hasMoreElements()) {
    NetworkInterface nic = interfaces.nextElement();
    Enumeration<InetAddress> addresses = nic.getInetAddresses();
    while (hostName == null && addresses.hasMoreElements()) {
      InetAddress address = addresses.nextElement();
      if (!address.isLoopbackAddress()) {
        hostName = address.getHostName();
      }
    }
  }
}

Answer 2

You will need to use the following function to get the remote address/hostname:

request.getRemoteHost();

Answer 3

sometimes the application returns the IP address instead of the name

As referenced from this SO answer:

The issue could be since request.getRemoteHost() does a reverse DNS lookup instead of taking it from the HTTP headers; if it fails to look up the DNS information using the IP, it returns the IP address as a String.