Need help getting DB2 Connect to catalog a remote AS400 DB2 server

[fahrvergnuugen]

Here's the situation:

I'm trying to get DB2 Connect, running on a linux web server, to connect to a backend DB2 database, running on an iSeries AS400.

I am 100% green when it comes to AS400s and DB2... so keep that in mind.

Here's what I've tried:

db2inst1@acc-intranet2:~> db2 catalog tcpip node nd1 remote rochester.atlascopco.net server 50000
DB20000I  The CATALOG TCPIP NODE command completed successfully.
DB21056W  Directory changes may not be effective until the directory cache is 
refreshed.
 
db2inst1@acc-intranet2:~> db2 catalog database TBIPRODD at node nd1 authentication server
 
db2inst1@acc-intranet2:~> db2 connect to TBIPRODD user tbiweb using ********
SQL30081N  A communication error has been detected.  Communication protocol 
being used: "TCP/IP".  Communication API being used: "SOCKETS".  Location 
where the error was detected: "10.48.1.7".  Communication function detecting 
the error: "connect".  Protocol specific error code(s): "111", "*", "*".  
SQLSTATE=08001

Now I figure that error means that it failed to connect via port 50000 (which I read somewhere is the default port). I can't telnet to that port either, so it's definitely not open.
What do I have to do to prepare the AS400 to receive connections from DB2 Connect?