[Danny]

Код:

public OnPlayerConnect(playerid)
{
        new ip[16];
        GetPlayerIp(playerid, ip, 16);
        if(playerid == MAX_PLAYERS-1 && strcmp(ip, "[your ip here]", true))
        {
                Kick(playerid);
         }
         return 1;
}

Maybe I missed something here, but I guess this is the basic way to do something like this.