This week I've been writing a WebSub hub. It's server program that receives subscription and publish requests and sends notications to the subscribers when a website changes. The website itself sends a request when the website changes. This way the subscribers know when to update their feeds.
Implementing the server is quite simple, especially with the help of a website that checks your implementation, websub.rocks.
WebSub Rocks! is a validator to help you test your WebSub implementation. Several kinds of tests are available on the site.
By reading the spec and following the steps from websub.rocks, it was quite simple. The problem is that not all websites implement this exact specification. FeedBin, for example, implements a feature from an older version of the spec and won't validate the subscription, when it otherwise would be good. A small change makes me support it, but I also send a commit to the FeedBin software on Github. That removes that use of the feature. As expected, this change leads to more changes, so we will see how this pans out.