Following the GameSpy server shutdown in 2014. NecroVisioN can no longer be played online natively. OpenSpy[openspy.net] is an open source GameSpy emulator that fully supports the multiplayer functionality of this game, and many others.

The simplest method of getting NecroVisioN's multiplayer functionality restored is through the use of a pre-patched Engine.dll file where all GameSpy domains are changed to OpenSpy ones.

Download the following file[drive.google.com] and extract it to the bin folder in your game directory overwriting the file there. To navigate to the game directory on the Steam version, select NecroVisioN in your library, right click on it and hit properties, then select browse under the local files tab.

You can also manually edit your dll file with a hex editor such as HxD[mh-nexus.de]. Navigate to the Bin folder in your NecroVisioN install and open Engine.dll with your hex editor.

The only edit you need to make is replacing all references to "gamespy.com" with "openspy.net". In HxD, the replace tool is accessed through the search tab. Set data type to "Text-string" & Search direction to "All", then click replace all.
Now save.

This method is not recommended as the IP addresses of the various OpenSpy servers are currently prone to change. If the IPs in this guide are outdated, please let me know.

Open your hosts file located in with a text editor such as notepad running in administrator mode, then add the following lines and save.

Once NecroVisioN has been patched to use OpenSpy (or the lines were added to your hosts file), you will be able to host and join games again from the menus, as well as host dedicated servers using the server executables. No port forwarding is necessary as NecroVision has natneg support.