#!/bin/bash
while :; do ncat -4 -z -u -w 10 $SERVERURL $SERVERPORT && \
knock -4 -d1000 $SERVERURL 51831:udp 51833:udp 51830:udp || break; done
knock -4 -d1000 $SERVERURL 51830:udp 51833:udp 51831:udp