nmap port scan for vpn and proxies

Question

I am trying to detect the vpn and proxies from the iplist so is anyone know the fastest and reliable scan command for nmap? right now I am using this

nmap -sS -sU -T4 -A -v -PE -PP -PS21,22,23,25,80,113,31339 -PA80,113,443,10042 -PO --script all $IP