So, while looking for a quick and easy FTP server analog to this popular Python trick:

$ python -m SimpleHTTPServer
Serving HTTP on port 8000 ...

I found a Stackoverflow post that shows Twisted has a one line FTP and more:

$ twistd -n ftp

The -n option is for “nodaemon”; don’t daemonize and run in the foreground.

Just looking at the options for twistd, it looks like you can also do port-forwarding, SOCKS tunneling, a HTTP server, a DNS server, and more.