Unary RPC

Client sends a single request to the Server and gets a single response back, just like a normal function call.

Server Streaming RPC

Client sends a single request and server sends a stream of response. The client reads from the returned stream until there are no more messages.

Client Streaming RPC

Client sends a stream of data and gets a single response back. Once the client has finished writing the messages, it waits for the server to read them and return its response

Bidirectional Streaming RPC

Both client and server send stream of data. The two streams operate independently, so clients and servers can read and write in whatever order they like.