Bi-directional gRPC Calls

A bi-directional call in gRPC allows us to stream data from the client to the server and from the server to the client. Both of these processes can be completely asynchronous. This process is useful in scenarios where both the client and server should be able to send messages to each other asynchronously. For example, when we're using a messenger app, we can send messages whenever we want and receive messages at any time. Opening a stream from both the client to the server and from the server to the client allows us to send messages in both directions without having to initiate a full request every time we want to do it.