Net packs are simple structures used to transmit information between client and server. They are defined in netpacks.h file. Packs can be applied to both client and server. The comunication with use of net packs is obligatory even in offline mode.
Packs for client
Sent to client in NetpacksClient.cpp, result in change of player interface, such as dialog pop-up or battle stack animation.
Packs for server
Sent to server, result in change of game state. Their behavour is defined in NetPacksLib.cpp file.