# A Unary RPC End to End — gRPC

Source: https://www.skillbyai.com/en/grpc/s-unary

> Server and client in Python.

## Implement the servicer, call the stub

On the server, subclass the generated servicer, implement each method (receiving the request message and a context), register it with a server, and listen on a port. On the client, create a **channel** to the server address and call methods on the generated **stub**, ideally with a deadline. Errors are reported by aborting with a status code on the server and raised as `RpcError` on the client.

## A Python server and client

A sketch using grpcio; production servers need TLS.

```python
# server.py
from concurrent import futures
import grpc
from gen.shop.v1 import order_pb2, order_pb2_grpc

class OrderService(order_pb2_grpc.OrderServiceServicer):
    def GetOrder(self, request, context):
        order = repo.find(request.id)
        if order is None:
            context.abort(grpc.StatusCode.NOT_FOUND, f"order {request.id} not found")
        return order_pb2.Order(id=order.id, total_cents=order.total_cents, currency="INR")

server = grpc.server(futures.ThreadPoolExecutor(max_workers=16))
order_pb2_grpc.add_OrderServiceServicer_to_server(OrderService(), server)
server.add_insecure_port("[::]:50051")   # local development only
server.start()
server.wait_for_termination()

# client.py
with grpc.insecure_channel("localhost:50051") as channel:
    stub = order_pb2_grpc.OrderServiceStub(channel)
    order = stub.GetOrder(order_pb2.GetOrderRequest(id="o-1001"), timeout=2.0)
```

## Never ship insecure ports

add_insecure_port and insecure_channel are for local development; use TLS credentials everywhere else.

**Quiz:** How does a Python gRPC server report "not found"?

- [ ] Raise HTTP 404
- [ ] Return None
- [x] context.abort with StatusCode.NOT_FOUND
- [ ] Print an error and return an empty message

*Answer:* context.abort with StatusCode.NOT_FOUND. Status codes, not HTTP codes.