Here's a break down of what ports go to each program on the server side:

     Port Protocol   Program Name    Program Description
       23   TCP      bnetd           Telnet Connection Support
     4000   TCP      d2gs            Diablo II Closed Game Server
     6112   TCP/UDP  bnetd           Basic Battle.net (TM) Chat & Game Initialization
     6113   TCP      d2cs/d2closed   Diablo II Realm Server
     6114   TCP      d2dbs/d2closed  Diablo II Database Server
     6114   UDP      bntrackd        Tracking Daemon for Producing Stats
     6200   TCP      bnetd           Warcraft III Router
     6667   TCP      bnetd           IRC Connection Support

Here is a break down of what games uses what port on the client side:

     Game Name                               Port Number(s)
     Warcraft II Battle.net (TM) Edition (BNE)  6112
     Warcraft III Reign of Chaos                6112, 6200
     Starcraft                                  6112
     Starcraft Brood War                        6112
     Diablo                                     6112
     Diablo II Open Battle.net (TM)             6112
     Diablo II Closed Battle.net (TM)           6112, 4000