RPC types
Now that we know that there are four RPC operations, we can see how they are combined to create the different RPC types that gRPC provides. We will talk about the Unary, Server Streaming, Client Streaming, and Bidirectional RPC types. We will see that each type presented is a combination of the RPC operations presented earlier.
Unary
A unary RPC is an RPC that performs one request and returns one response. We already touched upon this in the previous section, but let us go ahead and make the process clearer.
As always, the first step is the client sending the initial header. This header will contain the information related to the RPC endpoint that we want to invoke. As of this point in the book, we simply need to know that this mostly includes the RPC route and the stream ID. The former is to let the server know which user code function it should call to process the request. The latter is a way to identify on which stream the data should be sent. This is because...