Enable Firewall Rule receiving UDP-Packet with content "ONF"

RouterOS Beginner Basics
1

Hi,
it is possible to enable a specific Firewall rule receiving a UDP-Packet on the Port 9999 with the content “ON”?

2

Something is possible. If you want “ON” (case-sensitive) anywhere in packet, you can use this:

/ip firewall filter
add action=accept chain=forward content=ON dst-port=9999 protocol=udp

For whole packet containing only “ON” and nothing else (but case-insentitive, so even “on”, “On” or “oN” will match), use this:

/ip firewall layer7-protocol
add name=ON regexp="^ON\$"
/ip firewall filter
add action=accept chain=forward dst-port=53 layer7-protocol=ON protocol=udp