My “SFTP Server/Client” is now functional with “resume” (reget/reput to resume incomplete transfers), retries with timing (retry transfers n times, every x seconds), and integrity checks (checksums).
Each transfer use streams to avoid too much memory consumption and to speed up the checksum checks (calculated at the same time as the transfer by using pipes) .
I got rid of every SFTP client dependencies mentionned above (but they greatly inspired me) and the SSH/SFTP functions used are now Erlang :ssh_sftp calls.
I only kept the elixir_uuid library (needed to generate unique ID for each transfer) and the logger_file_backend library to log to a file.
I use ETS/DETS to keep track of failed tranfers.
Unfortunately, I can’t publish my code on Github as it is part of a corporate application.
Jaypee
Phillipp
Can’t you just put it into a library and sell it to the management as “giving back to the community”? Companies these days mostly use OSS software so it’s only fair to give back every now and then. It’s also great (and basically free) marketing, plus you get improvements and bug reports from the community.
Jaypee
I will ask but there’s few chance…
Anyway I would have to seriously clean my code beforehand as it’s a “learning” one: full of Elixir n00b’s “scories” ! 
Jaypee
I’ve got official confirmation by my managers that I’m not allowed (at least for the moment) to publish my code.
Anyway, I will remain at the disposal (in this thread) of anyone who struggles with such SFTP problems with Elixir…
Jaypee
I redevelopped an entire new application (“Simple SFTP Client Server in Elixir”), based on things I learned this year:
Here’s the SscsEx GitHub page
NB: You can only use this repository as an inspiration for your own code as SscsEx will NOT be updated: I’m now on my way to the next Elixir step: learning Phoenix + LiveView ! 
Jaypee
New step now:
I’m currently developping a gateway to monitor my SSCS servers, using Phoenix/LiveView/Tailwind with the idea to fully use real time features (thanks to the Stephen Bussey’s new book) and minimal DB access (BTW, only a small ETS).
I have added a new module to the SSCS server to manage the Phoenix Channel communications (using MobileOverload Elixir Channel Client library) and the first results are encouraging !
To be continued…
Sanjibukai
I didn’t saw this thread back in the days and just noticed it now (appeared on top upon this message).
First, I want to congratulate you for trying hard achieving your goal!
The entire thread (with some others ones linked here and there) was great to read.
I’m interested to hear more..
Keep up the good work..
Jaypee
Some updates:
I have been working on my corporate app (not the SscsEx on Github) SFTP Server/Client using streaming, integrity checking and retries on error.
Inspired by the “Real-Tme Phoenix” book, I had the idea to create a Phoenix app to monitor in real-time my SFTP Client/servers with no or at least minimal database accesses
It uses Phoenix + LiveView + Bulma CSS + Surface in order to completely avoid JS. I only have a small DETS database to store the basics informations about my servers (no Ecto) grabbing the rest in real time, with Phoenix Channels.
I only added a new communication layer on my SFTP Servers/Clients using the PhoenixClient library and made minimal refactories.
At the moment it’s on a very crude state but it works !