Port 80

Steve Palocz spalocz "at" tgtsolutions.com
Wed, 15 Aug 2001 17:52:18 +0000


To quote from Joe Knapka:

OK, we want to connect to port (say) 2001. Since the port number is
5900+display number, that means we need to connect to display
-3899. You can't enter negative numbers, but you *can* enter a number
that is large enough to overflow the 16-bit port number when 5900
is added, and thereby result in the correct port number. This
works because WinVNC stores the port number as a 32-bit value,
and truncates it to 16 bits when it's actually used.

If you want to use the WinVNC propertied page to do it, then
for port 2001, the correct number is 65536-5900+2001 = 61637, so
enter 61637 in the WinVNC properties "Display Number" field. (Note,
65536 is 2 to the 16th power, which, when truncated to a 16-bit
value, is 0).

The WinVNC viewer seems to take display numbers outside of the
expected range (which is? I'm guessing 0-99) to be port numbers,
so to connect in this manner you can just use "hostname:2001".
Or you can use 61637+5900 = 67537: "hostname:67537". Same result.

If you want to use port 80, you need 65536-5900+80 = 59716 in the
WinVNC "Display Number" field, and connect to 65536+80 =
"hostname:65616". Note that in this case you *must* use
the large port number, since "hostname:80" would cause the viewer
to connect to port 5980.

You can also use REGEDIT.EXE to directly install the desired port
number in \\HKEY_CURRENT_USER\Software\ORL\WinVNC3\PortNumber - that
is, you can enter decimal 2001 in that location to make WinVNC listen
on port 2001; no arithmetic required.

I have tested all this, confirmed that it works, and sniffed the
network to be sure the correct port is used.

-----Original Message-----
From: owner-vnc-list "at" uk.research.att.com
[mailto:owner-vnc-list "at" uk.research.att.com]On Behalf Of Keyser Soze
Sent: Wednesday, August 15, 2001 10:50 AM
To: vnc-list "at" uk.research.att.com
Subject: Port 80


Has anyone managed to connect to a WinVNC server on
port 80?

I followed the instructions in the FAQ for setting a
negative screen number of -5820 (had to copy and paste
the number from notepad as the '-' key is unavailable
in the screen number field).

I then opened up 'any host - port 80' on my firewall
and mapped port 80 from the public external IP to the
private internal.  Got shields up! to scan my ports
and 80 is open now but I cannot connect from work
(firewall blocks outgoing traffic except port 80 http
I think).

Thanks in advance.

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