The Next Generation display numbers

Glenn Lovitz lovitzg "at"
Wed, 20 Mar 2002 22:07:23 +0000

Whoa... If you could do that there would be no need for any ports!!!! Only
one thing can listen to a single port.  This is not a *NIX issue -- it is a
basic TCP/IP Networking 101 issue that affects all OS's.

You can telnet to port 21 on a machine running FTP and see the welcome
message just as you can telnet to port 590x on your VNC server which will
respond with "RFB 003.003".  You can't ALSO run a telnet service on either
port 21 or 590x while running the other services, daemons, processes or
whatever you like to call them on your platform.  Your idea would require an
RFB-enabled browser.

Port 580x is used for HTTP and 590x for RFB only.  The only way around this
would be to run still another daemon (another program/transport layer) on a
specified port, say 570x, have it read the packet headers, and route packets
across the TCP layer to the correct ports 580x and 590x on for the
respective services of HTTP and RFB. This would add considerable overhead
and addition latency.  It would likely complicate the lives of people
running SSH tunnels as well.  So it is possible, but not really practical.

> -----Original Message-----
> From: owner-vnc-list "at"
> [mailto:owner-vnc-list "at"]On Behalf Of Alex K.
> Angelopoulos
> Sent: Wednesday, March 20, 2002 12:59 PM
> To: vnc-list "at"
> Subject: Re: The Next Generation display numbers
> That 1-port-per display issue is one of the things that struck me as
> particularly inelegant when I first encountered VNC; without knowing
> anything about the technical details behind it, I am guessing
> that it was
> motivated by some shortcut taken to simplify the original
> implementation.
> Going one step further, it might be nice if the next
> generation could also
> respond to HTTP queries on the same port by attempting to
> serve an applet -
> assuming that would not introduce excessive complexity  or
> security issues
> into the server side of the connection.
> Is that a theoretical possibility? The client currently looks for a
> plain-text RFB version number being passed to it from the
> server; I assume
> something analogous is done by the server when connecting to
> a listen-only
> viewer.  Since HTTP connections already do text requests, a
> plain connection
> attempt or one with a query keyword appended would seem to me
> to be able to
> communicate sufficient information for the server to decide
> what to do.
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