Touhou 12.3 Netplay "Connection Failed"

[MediumSoda]

So whenever I try to play online with anyone, whoever is the client gets a "Connection Failed" error. I think the problem is on my side because whoever I play against can fight other people. Is there anything specific that could cause this error? I've tried using Hamachi and direct IP.

[Esoterica]

Routers are typically the main offender.  If either side's using a router, you'll need to open port 10800 (or whatever port you decide to use) to play.