How does grpc achieve "bidirectional streaming rpc" like a websocket?

Question

Is this bidirectional stream native to http2? I looked at various http2 client. I couldn't find any example where it allows the client and server to establish a single connection and continuously push messages from both side.

(For http2 maybe on a lower level, the communications between client/server just had one tcp connection and all the request/responses are multiplexed in it, but from application level can't find any example where you establish a single connection object, and that connection object can be reused to push messages to each other).

So how did grpc achieve "Bidirectional streaming RPCs"? Specifically in this document https://grpc.io/docs/what-is-grpc/core-concepts/ It indicates that the server side could define a Bidirectional streaming RPC, and it allows both the client and server side to continuously push messages, and achieve features that is websocket like.

Answer 1

Yes, bidirectional streaming is native to HTTP/2. You can read RFC-7540 for the details of how the protocol works, but basically it allows you to create several streams on a single TCP connection, and each stream can send data in either direction independently of each other.

I'm not familiar with all of the HTTP/2 libraries out there, but I know that nghttp2 will allow this in C++, and I think Java and Go have HTTP/2 implementations in their standard libraries.