Changing port number while passing through router

I'd like to do demonstrations of some software using VNC, which uses
port 5900.

Unfortunately, most of my clients are behind serious firewalls that
block most ports. However, very few block port 23 (telnet).

Thus, I'd like to translate port 23 (external) into port 5900
(internal) and pass it to my VNC server.

With an old Linksys BEFSR41, I was able to do that with UPnP
forwarding. New routers seem to be smarter and only allow this sort of
forwarding with real UPnP devices, not my simple Linux server.

I've been unable to reconfigure the VNC server to use port 23.

How can I get a new router and still forward external port 23 to
internal port 5900?

I'm totally stumped.

Thanks for any helpful suggestions.

Harry cried out

> I'd like to do demonstrations of some software using VNC, which
> uses port 5900.
>
> Unfortunately, most of my clients are behind serious firewalls
> that block most ports. However, very few block port 23 (telnet).
>
> Thus, I'd like to translate port 23 (external) into port 5900
> (internal) and pass it to my VNC server.
>
> With an old Linksys BEFSR41, I was able to do that with UPnP
> forwarding. New routers seem to be smarter and only allow this
> sort of forwarding with real UPnP devices, not my simple Linux
> server.
>
> I've been unable to reconfigure the VNC server to use port 23.
>
> How can I get a new router and still forward external port 23 to
> internal port 5900?
>
> I'm totally stumped.
>
> Thanks for any helpful suggestions.
>
>

I have no problem doing this without UPnP. I have UPnP disabled on
my router but am still able to foward a certain port number to 80 in
the inside for my printer, yet not have the very vunerable 80 open
externally. e-mail me and i will help if i can
roscoNOCAPS111atNOcharterCAPS.net