It is a good idea to report the important game events to the outside. This can be done by letting the game server send a LOG message to ggzd, so that it gets recorded according to the server configuration. It might end up in a log file, in a debug console or nowhere at all.
Other than that, there's not too much happening between game server and ggzd in this phase of the game, for most communication will happen between game server and game client. However, if a player leaves or another one wants to join and can't because a bot occupies the seat, the game server can request to change the seats on the table. To change the seat number, a NUM_SEATS request is sent. To boot a player, the BOOT request can be used. Finally, bots can be inserted and removed using the BOT and OPEN requests.