Hello, I've been using an implementation of server and client sockets based on WebSocketSharp. That's all I really need for the game I'm making. [ The implementation comes as part of this MasterServer Framework Asset: https://assetstore.unity.com/packages/tools/network/master-server-framework-71391 , or its GitHub equivalent, since it went open source. ] I've already built a server and client on my project around 1 and a half years ago, on Unity 2017. It worked after I lifted some security (firewalls) and opened my ports. I re-implemented this in Unity 2019. It works locally (I can connect to a server existing in the same scene as a client, using 127.0.0.1), but my team can't connect to the game remotely from their PCs, even though I have opened the ports (and provided them with my public IP). The strangest thing is that sites such as https://portchecker.co/check that let you check your ports find that my specified port when the server is running is open. I'd really appreciate any insight on the situation. Definite changes are that I'm currently in Unity 2019 and that I'm using the Unity Hub. The best I could narrow down to is this. There seems to be an issue based on Unity Versions. If I'm using Unity 2019 (any) as Server and Client, connection won't be established. If I'm using Unity 2017 as Server and 2019 as Client, it doesn't connect. If I'm using Unity 2019 as Server and 2017 as Client, it connects. If I'm using Unity 2017 as both Server and Client, it connects. Both 2019 an 2017 connect locally. Thanks a lot in advance!