Heya Bernard,
Welcome to our forums and many kind thanks for your interest in our network library.
Any packet handlers that are added using NetworkComms.AppendGlobalIncomingPacketHandler will be active for any current and/or future connections. Connection.AppendIncomingPacketHandler will only be active for the corresponding connection object.
If you would like to be able to change the types at runtime the simplest solution is to send and receive raw byte arrays, i.e. byte[]. You can then do the type conversion manually yourself.
Regards,
Marc