func callInternal(srcName string, from echo.Caller, opts echo.CallOptions, send sendFunc) (echo.CallResult, error) {
	// Create the proto request.
	req := newForwardRequest(opts)
	sendAndValidate := func() (echo.CallResult, error) {
		responses, err := send(req)

		// Verify the number of responses matches the expected.
		if err == nil && len(responses) != opts.Count {