Countries still block websockets from other countries. We don't use pure websockets because AJAX polling still works even when firewalls and other hardware stop websockets.
You shouldn't have any problems with firewalls so long as you use TLS. And if you don't use TLS and rely on XHR fallback, then you're suffering a downgrade in speed and latency.
We tried switching from SockJS to pure websockets and had to revert because it broke too many users, even though our website only supports WebGL (IE11, etc) and all communication is done over https/wss. One of the biggest problems was plugins like the zenmate privacy plugin https://chrome.google.com/webstore/detail/zenmate-security-p...
> Even over TLS? Are your connections being MITMed?
Some corporate networks do MITM you and mandate HTTP only (we've seen this surprisingly often in the wild).
Now, for most apps this isn't a concern since those employees probably wouldn't be allowed to use the app, but it can be quite important for apps that specifically target large businesses.
