Configure Fiddler to show sites that use non default ports

Hi, Ian--

You can easily flag traffic going to a non-default port in Fiddler; simply click Rules > Customize Rules. Inside OnBeforeRequest, add code like:

   if ( (!oSession.isHTTPS && (oSession.port != 80)) ||
        (oSession.isHTTPS && (oSession.port != 443)))
  {
     // Traffic isn't going to default port. Flag it.
     oSession["ui-backcolor"] = "red";
  }
  else
  {
    // Default port. Uncomment next line to hide if desired
    // oSession["ui-hide"] = true;
  }

Now, your second question is a bit more complicated. The first thing to recognize is that Fiddler is itself a proxy, so if traffic somehow bypasses a proxy, it will never go to Fiddler to begin with. Having said that, in a properly functioning browser, a site does not have any way to send traffic that bypasses a proxy-- in general, only a bug in the browser or in one of its extensions can cause traffic to bypass the proxy. There are a few corner cases where such behavior is explicitly designed into an extension (e.g. some types of video streaming in Flash) but most of those will fall back to going through a proxy if a direct connection is blocked by a firewall.

Regards,
Eric Lawrence
Telerik