You probably specified a different port in the connection window, then. The server list maps to the UDP source port received by the master server, and if you’re behind a NAT device that device is to blame for mapping the port differently. Normally it doesn’t take the TCP mapping along with it, though.
If that is actually your server, it seems it sends a TCP RST packet after requesting the HTTP data - are you on the right Mono version and do you not have a somehow-weird networking setup?
$ curl -v http://18.104.22.168:30120/
* timeout on name lookup is not supported
* Trying 22.214.171.124...
* TCP_NODELAY set
* Connected to 126.96.36.199 (188.8.131.52) port 30120 (#0)
> GET / HTTP/1.1
> Host: 184.108.40.206:30120
> User-Agent: curl/7.51.0
> Accept: */*
* Recv failure: Connection was reset
* Curl_http_done: called premature == 1
* stopped the pause stream!
* Closing connection 0
curl: (56) Recv failure: Connection was reset