Re: testing open ports on the user's side
On Friday 28 May 2004 15:59, Emma Jane Hogbin hurled the following on the
wire:
> On Thu, May 27, 2004 at 10:32:20PM -0700, Alvin Oga wrote:
> > > I'm working on a web site that includes streamed rich media files. I
> > > need a way to test to see which ports the user can access if they're
> > > behind a firewall. I'm guess that I need to try and send them an object
> > > (a picture maybe?) on one of the ports I need information about and
> > > then see if the picture is received or not.
> >
> > any secure site will only allow port 80 or port 443 for web ...
>
> It's not the server I'm testing, it's the user. Some streaming video
> (RealPlayer) doesn't come through on regular ports so the client wants a
> little app that they can ping at the *user* to figure out if they should
> send RealPlayer or something else.
You will never be very successfull if you try to connect to a port on the
client. Any client with an adminitstrator with half a brain will only allow
incoming traffic that is part of a connection that originated on the client.
(so called statefull filtering) With some exceptions like bootp.
Furthermore any client that's behind a device that does NAT is unreachable.
A client receiving data on a port and a client being reachable and listening
on a port are 2 different things. Even if the client is open on the internet
(no firewall or NAT) when you connect to it, you can only see if it sends you
a RST since that port will be closed.
I really think you'd better let them try to see if it works.
joost
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