You know kind of like you type "/members" and it displays a list in the chat box
To one person or everyone?
messageAll("","Message here.");
messageClient(gameconnection,"","Message here.");
of course, change gameconnection to the client you're sending the message to. Something like %client or %this (in gameconnection functions), or %player.client, maybe even %obj.client.
Anything referring to a client.