[15.37] Multiplayer Suddenly Not Working

[Grigorie]

Been playing with my buddy back home for the past few days, no issue. Today, I host, and he can't connect to me. So, I have him try to connect to other servers; works fine. I can't connect to anything, though!

Trolled through all posts about it, but I keep getting "Couldn't establish network communication with server" when trying to connect to anyone or anything on multiplayer.
I've forwarded the ports in my router and my firewall, still nothing. It was literally working fine yesterday and all the time before. Just today, this has become an issue, and I can't find ANYTHING beyond "forward your ports."

Tried going directly through IP, server list, any of that, nothing seems to work. I hadn't had any sort of issues before today, and we've both had zero changes to our routers and ISPs before today, so I can't possibly fathom why this is happening to me out of nowhere. Any help is greatly appreciated.

[Grigorie]

As an aside, something that got lost in my post since I was diddling with my router and lost what I had originally typed up; When I try to host, it tells me "Failed to determine external IP address."

My External IP address is static, though.. And, again, all of this was working fine yesterday. I have UPnP enabled, there is no port randomization, either..

Router is a Netgear WNDR4300, by the way.
Windows 10

[Loewchen]

When ever you try to communicate with anything you receive the answer way too late, this could be simply caused by a congested network. Try pinging the servers via command shell to rule that out.