2.2.2.1 Dispatcher Request Tag Payload

The Dispatcher Request tag payload precedes all DSLR remote service request tags and payloads. (DSLR service requests are children of the Dispatcher Request tag.) It includes all information relevant to calling a remote function on a specific service: the type of request that is being made (either a one-way event or two-way request), the service on which the request is being made, the service-defined function to be called on the remote service, and a one-time unique request handle to identify the specific request.

The format for the Dispatcher Request tag payload is as follows:

0	1	2	3	4	5	6	7	8	9	1 0	1	2	3	4	5	6	7	8	9	2 0	1	2	3	4	5	6	7	8	9	3 0	1
CallingConvention
RequestHandle
ServiceHandle
FunctionHandle

CallingConvention (4 bytes): An unsigned 32-bit integer that indicates the type of request (either a two-way request or a one-way event). This field MUST be set to one of the following values. (Note that for the dispenser service calls, CreateService and DeleteService, this value MUST be dslrRequest. See sections 2.2.2.3 and 2.2.2.4 for more details about CreateService and DeleteService.)

Value	Meaning
dslrRequest 0x00000001	DSLR Two-Way Request
dslrOneWay 0x00000003	DSLR One-Way Event

RequestHandle (4 bytes): An unsigned 32-bit integer.  A client allocated handle to uniquely identify this specific request.

ServiceHandle (4 bytes): An unsigned 32-bit integer. The service handle that uniquely identifies the service on which the request is being made. This service handle is allocated by the client as part of the CreateService request. (Note that for the dispenser service calls, CreateService, and DeleteService, this value MUST be 0x00000000, which is the service handle for the dispenser service.

Value	Meaning
DispenserHandle 0x00000000	Dispenser service handle. Used only for CreateService and DeleteService messages exposed by the DSLR dispenser service.
GenericServiceHandle 0x00000001 — 0xFFFFFFFF	Generic DSLR service handle, generated by the DSLR client during the CreateService message for a given service.

FunctionHandle (4 bytes): An unsigned 32-bit integer. Function handle for the specific function being called on the remote service. This function handle is defined and exposed by the remote service that corresponds to the specified ServiceHandle. (Note that for the dispenser service calls, CreateService and DeleteService, these values MUST be 0x00000001 and 0x00000002 respectively.

Value	Meaning
CreateService 0x00000001	Create remote service. Used by the DSLR dispenser service.
DeleteService 0x00000002	Delete remote service. Used by the DSLR dispenser service.
GenericFunctionHandle 0x0000000 — 0xFFFFFFFF	Function handle for the specific function, defined and exposed by the DSLR service that corresponds to the specified ServiceHandle.