That’s kinda funny I guess. I just have the same issue and I kind of nailed it down to socketio dat not being able to resolve the domain.
what happens when you enter ip:port of the server directly and not use the domain? Does this then work
For now my work arround is running a small python app running python-socketio,ewhich cconnects without problem and relaying the messages to a tcpDAT in Touchdesigne.