In synchronous RPC, a client makes a remote call and the call returns with either a success or failure code. Asynchronous RPC provides more opportunities for a call to fail, and these failures are handled differently depending on where and when they occur. The following table describes the ways in which a call can fail, and how it is handled.
| Source of Failure | How Handled |
|---|---|
| Client call to remote function fails. | The call raises an exception. Neither the client nor the server must call RpcAsyncCompleteCall. |
| Client call to remote function fails because of a failure in the asynchronous mechanism. | Client receives a "call complete" notification. RpcAsyncCompleteCall return value is the failure code. |
| Client issues cancel (either abortive or non-abortive). | Server learns of cancel by calling RpcServerTestCancel. Server must still call RpcAsyncCompleteCall or RpcAsyncAbortCall to complete the call. |
| Client issues an abortive cancel. | Client receives "call complete" notification. When client calls RpcAsyncCompleteCall, function returns RPC_S_CALLED_CANCELLED, unless the call failed, or completed before it was cancelled. |
| Call fails before server dispatched it. | Failure handled by run time and client and server stubs. |
| The synchronous portion of the manager routine raises an exception. | Run time catches exception and propagates it to the client. |
| Call fails after server calls RpcAsyncCompleteCall. | Run time handles it; server is not notified. |
| Special Error Handling Cases for Pipes: | |
| Client calls push and call fails. | Push returns a failure code. Client must call RpcAsyncCompleteCall. |
| Client calls RpcAsyncCompleteCall before the in pipes are drained. | Call fails with the appropriate pipe-filling error code. |
| Client calls pull and call fails. | Pull returns a failure code. Client must call RpcAsyncCompleteCall. |
| Either client or server calls push or pull in the wrong order. | Run time returns pipe-filling error status. |
| Server calls push and call fails. | Push returns a failure code. Server must call RpcAsyncCompleteCall. |
| Server calls RpcAsyncCompleteCall before the pipes have been drained. | The pipe call returns a pipe filling error status. |
| After the dispatch, a receive operation fails. | The next time the server calls pull to receive pipe data, an error is returned. |