A minimalist, mostly RFC 959 compliant, asyncio FTP server

[DavesCodeMusings]

FTPdLite

I've been working on an async FTP server and I thought I'd share. It's mostly for my own education, but it could be useful for some folks.

What is it?

A minimalist, mostly RFC 959 compliant, asyncio FTP server for MicroPython-based microcontrollers.

How do I get it?

You can use mpremote mip install github:DavesCodeMusings/ftpdlite

Or you can visit the project site at https://github.com/DavesCodeMusings/ftpdlite/

For the love of God, man... why?

FTP is one of the earliest internet protocols. It's a security nightmare, but it's a pretty straightforward way to get files from point A to point B. And MicroPython asyncio is something I've been interested in learning more about. So, why not?

Plus, There's only about nine and a half hours of daylight this time of year. I need something to keep my sanity.

What else is there?

It's probably got bugs I don't know about, but for the case of a single user uploading and downloading files, it works. Tested clients include: FileZilla (with simultaneous connections set to 1), curl, wget, and tnftp. (Windoze ftp.exe works too, but not behind a firewall.)

Using asyncio means it does handle multiple sessions, but only one session per client IP address. So still limited in some ways.

There are some extra features built into the SITE command. Together with the tnftp client's extra commands, it makes for a rather sublime remote file management experience. The sample session below demonstrates some of the functionality.

Sample Session

pi@raspberrypi:~ $ man ftp | head -5
TNFTP(1)                  BSD General Commands Manual                 TNFTP(1)

NAME
     tnftp — Internet file transfer program

pi@raspberrypi:~ $ ftp 192.168.10.57
Connected to 192.168.10.57.
220 FTPdLite (MicroPython)
Name (192.168.10.57:pi): Felicia
331 Password required for Felicia.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> pwd
Remote directory: /
ftp> ls
227 Entering passive mode =192,168,10,57,192,8
150 /
-rw-r--r--  1  root  root         629  Jan  1  2000  boot.py
-rw-r--r--  1  root  root         156  Jan  1  2000  config.py
-rw-r--r--  1  root  root         564  Nov 18 01:06  device_specs.py
drwxr-xr-x  1  root  root           0  Jan  1  2000  lib/
-rw-r--r--  1  root  root         117  Nov 18 01:06  main.py
drwxr-xr-x  1  root  root           0  Jan  1  2000  pub/
226 Directory list sent.
ftp> cd /pub
250 /pub
ftp> ls
227 Entering passive mode =192,168,10,57,192,1
150 /pub
-rw-r--r--  1  root  root     3407402  Nov 18 01:12  Rick_Astley_-_Never_Gonna_Give_You_Up.mp3
-rw-r--r--  1  root  root          21  Nov 18 01:06  test.txt
226 Directory list sent.
ftp> less test.txt
This is a test file.
ftp> site df
211-Filesystem        Size        Used       Avail   Use%
211-flash          6144KiB     3428KiB     2716KiB    56%
211 End.
ftp> site free
211-         Total       Used      Avail
211-Mem:    133KiB      52KiB      80KiB
211 End.
ftp> site gc
211 OK.
ftp> site free
211-         Total       Used      Avail
211-Mem:    133KiB      26KiB     106KiB
211 End.
ftp> rstat
211-FTPdLite (MicroPython)
211-System date: Nov 18 15:43
211-Uptime: 0 days, 01:25
211-Number of users: 1
211-Connected to: ftpdlite
211-Logged in as: Felicia
211-TYPE: L8, FORM: Nonprint; STRUcture: File; transfer MODE: Stream
211 End.
ftp> quit
221 Bye, Felicia.

Edited 19 Nov 2023 to say FileZilla is now working. And multiple user accounts possible. Woohoo!

[peterhinch]

Nice work! If you can get it working with FileZilla we'd have a useful GUI tool for file management on local devices.

[robert-hh]

Glad it helped. The code I reference uses as well an empty string (besides \r\n) as quit signal, with similar concerns. I added the following comment:

            if len(data) <= 0:
                # No data, close
                # This part is NOT CLEAN; there is still a chance that a
                # closing data connection will be signalled as closing
                # command connection
                log_msg(1, "*** No data, assume QUIT")
                close_client(cl)
                return

[DavesCodeMusings]

Thanks again, @robert-hh

This was the final piece of the FileZilla compatibility puzzle. I can now log in, list remote directories, download a file, and quit... all in PASV mode from behind a firewall.

[skyguy]

If you modify the parameters of your run method like this:

def run(self, host="0.0.0.0", port=21, loop=None, debug=False):

then it will listen on all interfaces automatically, so that it can be started with just:

server.run()

[DavesCodeMusings]

Thanks @skyguy . I've made the change.

[DavesCodeMusings]

And, I had to revert it. I need the host address to send the connection info in the response to a PASV command. With 0.0.0.0 as the host, it doesn't work.