I have a test application running at test.rsscloud.io on ports 80 and 9876.
The following code works:
curl --location --request POST 'https://brokenriverbooks.com/?rsscloud=notify' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'domain=test.rsscloud.io' \
--data-urlencode 'port=80' \
--data-urlencode 'path=/feedupdated-s8759' \
--data-urlencode 'registerProcedure=' \
--data-urlencode 'protocol=http-post' \
--data-urlencode 'url1=https://brokenriverbooks.com/feed/'
However if you change the port to 9876 it fails. For some reason the rssCloud plugin seems unable to hit ports that are not 80.
@josephscott @andysylvester --
Once I got the FeedLand implementation working with WordPress and @andrewshell's server, I created a very simple demo app that just does the rssCloud functionality in FeedLand anyone can test with our implementation, and see exactly what's going on. MIT License.
https://github.com/scripting/reallysimple/tree/main/demos/clouddemo
It also provides a reference implementation for people just getting started.
At some point I need to rewrite the walkthrough. It's not very well done imho (I am the author).