[0.15.28] Headless server on MintOS, client fails to connect

[Pixelguru]

I've been trying to set up a headless 0.15.28 server on Linux Mint (Cinnamon, Sonya, latest stable release)
I have verified that the port, 34197, is forwarded, opened, and cleared by the firewall, and has a stable IP.
In case it helps, my wifi is provided by Xfinity.
The server runs fine. However, on any attempt to connect, I'm faced with an error:

Code: Select all

Couldn't establish network communication with server.

Note, the same error comes up when trying to connect to a nonexistent server.
I've been searching for several days, all similar errors appear to be p2p and easily solved by running the game client - this is obviously a problem for a dedicated server.
I have attempted to test using v. 0.14.23, the same error occurs, plus a notice that the matching server confirmed it with the wrong address.
Any help would be greatly appreciated. Thank you.

PS: I will provide logs shortly, after I get back to my linux machine.