Client command line joining:

/internet 		Must be specified to join an internet game (that is, not a lan server)
/join=serveradress	The adress with optional port of the server to join, or the server name.	

optional parameters:
/login=login		Account login to be used to play online.
/password=xxx		Account password
/serverpassword=xxx	If a password is needed to join the match

If any of these parameters is missing, the game will ask them to the player.

parameters to allow more remote controlling:
/silent			Skip news... to allow joining a server without user interraction
/team=xxx		("red" or "0" / "blue" or "1") -> set the default player team
/nickname=xxx		Force nickname
/profile=xxx		Force using a specific profile on disk. (to avoid the profile choice dialog)
/key=xxx		Key to use for profile creation.

If not specified, the nickname used is the one stored in the online account.