Ok, well initially I just opened 2049 from the server to receiver for TCP, which didn't work. Then I changed it to all three protocols, and it worked. I tried rebooting my server computer just to test the robustness, though, and now it won't work again. Any idea why rebooting the server caused it to revert back to the previous behavior?

I'll try opening those two ports in the opposite directtion as well and report back with what happens.