Proxy ping event to persuade players to use new IP.

ProxyPingEvent.java

@EventHandler
public void onPing(ProxyPingEvent evt) {
    ServerPing ping = evt.getResponse();
    InetSocketAddress hostAddress = evt.getConnection().getVirtualHost();
    String host = hostAddress == null ? null : hostAddress.getHostString();
    if (host != null && !host.contains("the-ip-you-should-use.net")) {
        ping.setDescription("You aren't using the new IP! Be gone!");
    }
}