[GD-General] Basic questions regarding networking games...

[Colin F. <cp...@ea...>]

2002 September 23rd
Monday

I have a few questions, but first I'll provide a hypothetical
context:


INTRODUCTION:
=============

  Let's say you have a small multiplayer game, and let's say
you want it to run on a LAN.  Let's say you start the server,
and later a client starts up, but the client doesn't know 
the IP of the server.

  Now let's say that the server has a preferred range of ports,
say: 32000, 32001, 32002, 32003, 32004.  (Only one available
port is actually used by the server, but the server will 
attempt to acquire a port from the range above, and clients
will know that a server could be running on one port within
this range.)

  The client can do a UDP broadcast on the subnet, say
192.168.1.255, to each of the ports in the preferred port range
of the server.

  The server can respond when it gets the client query.


QUESTIONS:
==========

  [A] For *Internet* games I assume service WWW sites like GameSpot,
etc, advertise the IP's and ports of game servers -- or you
can indicate the IP and port number of your server through
any other means (phone call, e-mail, chat, etc).

  QA1: Is this the dominant way to discover *Internet* games?



  [B] For Internet games the port(s) can be fairly arbitrary
(anything above 1024 and below 65536, right?), but for 
convenient "discovery" of servers on a LAN it might be nice
to have a few preferred port candidates to try -- instead
of broadcasting to all 64000 ports in a brute-force search.

  QB1:  How might one select "default" port ranges for the
convenience of LAN clients searching for servers?

  QB2:  Might a server on a LAN advertise itself periodically,
like once per second?...Perhaps only during the "join" phase of
a game (if players can't just jump in at any time)?
This sounds pointless when clients can essentially do
the queries as needed, but maybe when the server is on
a totally random port (but advertises itself on a known
port), it might make it easier for clients to discover
the server (just by listening on a known port for the
unsolicited broadcasts of the server).



  [C] Some applications have one "well-known" port for
initiating sessions and create ports for handling those
sessions.

  QC1: Sorry for my ignorance, but do you think it's okay
to have all clients send UDP to the same server port
for processing?  (So each UDP packet has a "Client ID"
to demultiplex the packets.)

  QC2: Even if all UDP traffic can go to a single server
port, do you think there might be some benefit to having
a seperate port that is strictly for joining the game?
(The "real" game might be some RANDOM port, but the
service for joining the game might be on the "well-known
port range".)

  QC3: To your knowledge, do many first-person shooter
deathmatch games just feature a single UDP port for
all game-related traffic?


I basically want to learn from the experience of others
regarding the basic mechanics of "discovering"
servers (Internet and LAN), choosing port(s), and 
choosing a total number of used ports for a single server.

--- Colin
cp...@ea...