For the 1 connection per IP, go into your server.java, and search this.
You should see something like this..if (num > {
if (num > 5) {
banHost(host, num);
return false;
}
Replace the number 5, to how many IP's you want allowed in your server at a time. If you want 1 IP address, just switch the 5 to a 1.
So it should look something like this..
I hope that helped.if (num > 1) {
banHost(host, num);
return false;
}