I have exactly the same problem. Which is:
- I'm running C2 as Administrator
- firewall is turned off
- other servers CAN be started on the same port and IP (for example HTTP server of TortoiseHG does that)
- local IP address pings succesfully
And even though I can see other servers work on port 50000 I still get 1232 error from Construct.
This is a complete mistery. And considering that I can make other HTTP server work on the same port and IP, it has to be a bug in Construct logic. I mean it works, I can see it. So why doesn't it work?
What I don't understand is why to check if the server is reachable at all? We do not want to do anything with a remote server, so it doesn't matter if it is reachable. Apparently there are some cases in Windows when a local server is considered unreachable.
I don't know if it helps, but when I type "arp -a" my IP is not on the list. But I can still ping it and run an HTTP server on it.
I'm really out of ideas how to fix the problem. Either I have to make my IP reachable or there must be some change in Construct.