How to know if the client is using http or http2?

I see in the nginx example that it can listen for both http and http2 calls, given two different ports:

server {
    listen 9091;
    listen 9092 http2;
    server_name localhost;
    location / {
      grpc_pass localhost:9090;
      if ($request_method = 'OPTIONS') {
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Transfer-Encoding,Custom-Header-1,X-Accept-Content-Transfer-Encoding,X-Accept-Response-Streaming';
        add_header 'Access-Control-Max-Age' 1728000;
        add_header 'Content-Type' 'text/plain charset=UTF-8';
        add_header 'Content-Length' 0;
        return 204;
      }
      if ($request_method = 'POST') {
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Transfer-Encoding,Custom-Header-1,X-Accept-Content-Transfer-Encoding,X-Accept-Response-Streaming';
        add_header 'Access-Control-Expose-Headers' 'Content-Transfer-Encoding';
      }
    }
  }

Does it mean that the JS grpc-web client knows how to upgrade to http2 if the given port is http2? If the given port when creating the client is the http one, how the grpc-web client can support the streaming features (server push for example)?

I’m not clear on this point,

thank you for your help!

[sulliwane]

Like this ?

May I ask why grpc-web is not using “modified grpc over HTTP2” when all browsers support h2?

Finally, if it’s not using h2, I’m curious to know how the server push is implemented over http1.1 (long polling?)

Many thanks

[sulliwane]

Got it! Many tanks