I have a website which is behind a severely restricted firewall, running on an environment where the IP address is private and not public. As such, all outgoing requests have to go through a firewall.
HTTP requests work well through the firewall, but HTTPS do not.
A year ago, a similar issue was reported here (and duly closed), mentioning that a simple tweak in the code would make JetPack attempt to connect via HTTP and ignore connections via HTTPS. It was a very simple change.
Later, an automatic fallback mechanism was introduced: JetPack would attempt to connect first via HTTPS, and if that failed, it would connect via HTTP. This meant that the initial connection might have taken a bit longer, but, eventually, it would connect without problems.
Recent versions, however, seem to work differently. If JetPack makes a HTTPS connection through a proxy, and that connection fails, it never falls back to HTTP. I believe it's assuming that the proxy knows what it's doing, and accepts the error from the proxy as being "final" and doesn't make any more attempts. In our particular setup, the proxy clearly cannot connect via HTTPS (and will drop an error!) but has no problem reaching jetpack.me or jetpack.wordpress.com via HTTP.
So what I need to do is to "force" JetPack to use only HTTP requests and never even attempt HTTPS ones. How is that managed? I've looked through the code and I'm baffled where the old fallback mechanism is nowadays. It looks like Automattic might have dropped HTTP connections, and, as such, just attempts HTTPS ones. Is that so?