[PRIVATE SERVER] Multiplayer security error [PRIVATE SERVER]

I have heard that others have this problem too. I hosted server with Hamachi and I disabled my firewall completely. Still my friend seems to get security error while connecting to nexus. He made account on his client and I found it in SQL database so at least something is happening.

your still further than any of us, did you edit the Localhost part in the client?, i just edited the 127.0.0.1:80, but editing the localhost might be the problem, like string 72 or somethin