You could do a lobotomized WebSockets implementation that was an extremely thin layer on top of http, similarly to this.
In this way SSE and WebSockets are exactly the same. They are HTTP requests that you keep open. To firewalls and other network equipment both look the same. They look like long lived http requests, because that is what they are.
In this way SSE and WebSockets are exactly the same. They are HTTP requests that you keep open. To firewalls and other network equipment both look the same. They look like long lived http requests, because that is what they are.