From Onset Developer Wiki
Early callback of when a client tries to connect to the server. Client is not fully authorized by the server in this state. You can return false in this event to disconnect the client immediately.
IP address of the client connecting.
Port of the client connecting. This is not the server port.
AddEvent("OnClientConnectionRequest", function(ip, port) -- you can check for blacklisted IP and return false to stop them! end)