Sometimes the game server can have several LAN cards (NIC) attached although only few of them allow the actual communication for gamers in the name of security.
In the case like this, you need to appoint which specific NIC that you will use. If not, client can connect to server but UDP or P2P communication may not perform appropriately.
You can appoint NIC through Proud.CStartServerParameter.m_localNicAddr parameter of Proud.CNetServer.Start. To gain the list of NIC local address, use Proud.CNetUtil.GetLocalIPAddresses.