Problem : some local client is making connection to an ftp server on the internet once a week and i would
like to capture that data on a file on my mikrotik.

Possible solution: Tools/packetsniffer:
Is it possible to sniff for packets coming from one of my lan or wlan clients with a destination port of 20 or 21 on the internet?

I would set the interface to the lan + wlan bridge but there is only 1 port setting is that the source port or destination port?

A config example would be great with a port setting.