I need to open port 54321 for an application running on my network. I have forwarded the port as I have many others with success; however the port just will not open. If I do an external port probe, it shows this port as being closed, where all the others I have created show open. Any ideas how I can further troubleshoot this please?

Have you tried the syslog to see if its matching the port?

Yes, I have monitored syslog and no traffic is passing through that port.

Some malware programs use this port to communicate- is it possible the Draytek is clever enough to stop all attempts to open this port?