My friend can't connect to my minecraft server

the error says " [Minecraft An Existing Connection was Forcibly Closed by the Remote Host. I saw the same issue here and am wondering if i need an ethernet cable (https://discuss.playit.gg/t/minecraft-an-existing-connection-was-forcibly-closed-by-the-remote-host-minecraft") I am also wondering if my server is actually working. I turned my modded singleplayer world into a server from watching a video, all I did was connect the tunnel to the app and turn on lan, I didn’t alter any settings except making my tunnel type java. I’ve heard this is a problem with internet, how can I fix this?

try checking if your tunnel is pointed to your local ip address and port of where your minecraft is running.