Postman, the application typically used for API development, doesn't have any support for Server-Sent Events (SSE), HTTP2, or Websockets. Additionally, there aren't a lot of streaming APIs to work with despite plenty of real-time apps.

Because there's such a dearth of tools, I worked these past few weeks with some friends to create a Streaming API development tool called Swell. If you're interested in contributing to that project the repo is here: https://github.com/getswell/getswell.

I'm also interested in general thoughts as to why these protocols aren't used more often.