The original article is a bit unclear on this, but the command was not directly received from a TCP connection initiated by the botnet owner.
Rather, his server connected to some IRC server and joined a channel with all his other bot friends. The owner then sent the command to the IRC channel, and it is then broadcasted to all bots by whatever IRC server he is using.
(This is why lots of IaaS providers will forbid you from hosting an IRC server, and sometimes block all IRC traffic (by port anyway) on their networks)
Rather, his server connected to some IRC server and joined a channel with all his other bot friends. The owner then sent the command to the IRC channel, and it is then broadcasted to all bots by whatever IRC server he is using.
(This is why lots of IaaS providers will forbid you from hosting an IRC server, and sometimes block all IRC traffic (by port anyway) on their networks)