New client for new server(software)?

I am the author of F*EX, an http based filetransfer service:

The (web)server is written in Perl for UNIX, it does not use any
additional webserver like apache or nginx.

https is handled via stunnel.

My development server has a standard certificate
from the provider of our university.

This particular service is limited to members of the University of
Stuttgart, but the software is free and anyone can download it and run a
server of its own. See

Other FEX admins with own servers might want to use letsencrypt
certficates. Therefore I should write an own F
EX letsencrypt client or
integrate the Linux certbot in some way.

There are lots of tutorials how to use certbot with common webservers like
apache or nginx, but this does not help me.

How can I integrate letsencrypt in my own server software?

In need some kind of HOWTO, tutorial for the bloody beginner, etc.

How do I start? Which documents can help me?

Hi @framstag,

Welcome to the community forum!

To get started writing your own client, please first take the time to read the integration guide at

If you want the F*EX webserver to request certificates and want to build a client, the existing known Perl based Let’s Encrypt clients at should provide more insight.

A potentially easier route would be using certbot with a DNS plugin. The dns-01 challenge would allow your server to request a certificate without needing to run a standalone webserver. Certbot can then trigger a pre-hook and post-hook which can be scripted to send a SIGHUP to the running stunnel process to gracefully reload the config/cert/key after issuance or renewal.


Maybe this can help?

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