Cant Join my Modded server

Ok I set up a server for me and my friend to play. It has 3 Mods:

ClaySoldiersMod-1.12.2-3.0.0-beta.2.jar
OfflineSkins-1.12.2-v6.jar
SanLib-1.12.2-1.5.1.jar

I have all 3 of those mods installed on my forge, and when I try connecting to the server, It says :

Connecting to the server
Logging i-
Failded to connect to the server. Disconnected

I have no idea what causes this, but I cant even join my own server.
Yes, I have all of the mods on my game installed and running

Logging in sometimes takes alot of time, But I get "timed out". And most of the time, it says "Logging in" like a milisecond after inmediately saying disconnected.