I need to check that an OpenVPN (UDP) server is up and accessible on a given host:port.
I only have a plain Windows XP computer with no OpenVPN client (and no chance to install it) and no keys needed to connect to the server - just common WinXP command line tools, a browser and PuTTY are in my disposition.
If I was testing something like an SMTP or POP3 servert I'd use telnet and see if it responds, but how to do this with OpenVPN (UDP)?
tls-auth
configuration option, then it is IMPOSSIBLE (If you don't have at least the outer wrapper key)! Any packet with incorrect HMAC signature will be discarded without response by the server.