`nstftp` consisted basically on reverse-engineering a custom network protocol (on the application layer) via a `.pcap` file with recorded interactions between a custom FTP client and server (hence the "ftp" in the name "nstftp"), and then creating a client that knows how to talk to that server to recover the original FTP server program to finally reverse-engineer it and find a dev-made backdoor to print the flag for us from the remote machine.

Full, detailed write-up can be found here: [https://litneet64.github.io/write-ups/dawgctf-nstftp/](https://litneet64.github.io/write-ups/dawgctf-nstftp/)