From Elendor
Syntax 1: +COM/JOIN <channel>
Syntax 2: +COM/JOIN/ALL
You must join a channel before you can speak on it or hear anything said on
it. Not all channels are available to you however. Each chat channel has a
lock which determines who can join. Some channels like the Public channel
are joinable by anyone. To see a list of the channels you may join, type
"+com/list". To see a list of the channels you are already on, type
"+com/on". To see a list of the channels which you can join and which you
are not already on, type "+com/off". To join one of these channels, use
the first "+com/join" command shown at the top of this help text.
<channel> is the full name of the channel you want to join (it is not
case-sensitive). To join all channels that you are allowed to join, use
the second command shown at the top of this text.
Example: +com/join public
+COM: You join the Public channel.