To add a bit more information to what the sibling post provides. The original WebSocket handshake is done over HTTP/1.1, there is an RFC specifying how to perfo

To add a bit more information to what the sibling post provides. The original WebSocket handshake is done over HTTP/1.1, there is an RFC specifying how to perform the negotiation also over HTTP/2 connection but its support lacking. On top of that, HTTP/2 itself can do full-duplex communication so it can be used as a replacement of WebSocket, no negotiation or protocol upgrade involved. This capability is rarely used though but is, for example, leveraged by gRPC which is able to do bidirectional streaming [1]. [1] https://grpc.io/docs/what-is-grpc/core-concepts/ https://grpc.io/docs/what-is-grpc/core-concepts/