Platform SDK: DirectX

Setup for Host Firewall Support Using an Application-Specified Fixed Port

To host a game through a firewall, the host must be using DirectX 6.0 or later, and the clients beyond the firewall must be DirectX 6.0 or later as well. To support applications using an application-specified fixed port n, a firewall administrator needs to allow an initial inbound TCP connection on port n, with subsequent connections of outbound TCP port n, inbound UDP port n, and outbound UDP port n.

Example of a Microsoft Proxy Server 2.0 configuration, where the application "SuperDuperGame" (superdg.exe) specifies the port as 12345.