Hi guys,
as my own RB is connected to ADSL (with draytek modem) and i get public IP on RB, decided to secure it as much as possible.
Here came port knocking with L7 strings as a password.
Due to lack of user-friendly software, i decided to write my own client - nothing very sophisticated, just an autoit script compiled to exe.
possibilities:
translation of domain name to ip address (requires actually working internet connection)
also takes ip address as an input (in case of no internet connection, just lan)
works from local network as well as from the internet.
asks for how many packets to send
asks for specific port number and string for each packet
port numbers and strings appear as ‘*’ while typing - for the safety of use in public areas.
after collecting all of that informations, it sends udp packets to our target system.
application as an attachment, if there will be anybody interested in source of it, can also publish original autoit script.
Published under creative commons CC-BY-NC-SA 3.0
If there will be some noticeable interest in this tool, i may add more options.
on my priority list is option to resend packets (in case if some of them got lost and didnt reach target)
possibly rewrite in some ‘more sane’ language.
there is a plan of creating php/ajax version working directly from web browser.
I’m also open for suggestions 
L7knock.zip (323 KB)