Polling the message queue

You can find out when a request arrives and then receive it in one of the following ways:

• Use the poll() or select() system call to detect the arrival of a request primitive, specifying the message queue identifier returned from the sl_register() subroutine. Then receive the primitive using the sl_receive_request() subroutine, specifying a timeout of 0.

  This method is recommended if the signaling process also needs to service other devices and needs a way to detect input from both its own devices and the signaling interface. If you use poll() or select(), note that the identifier is a message queue identifier not a file descriptor, and needs to be handled specially. See AIX Version 3.2 Technical Reference: Base Operating System and Extensions for details.

• Use the sl_receive_request() subroutine, specifying a positive timeout to block until a request arrives or a timeout occurs.
• Use the sl_receive_request() subroutine, specifying a negative timeout to wait indefinitely for a request to arrive.

If the return value is SLRC_OK, the request primitive is returned in the structure pointed to by psignalingRequest.

If the signaling process does not recognize the primitive, it should behave as described in Unrecognized primitives.

After processing the request primitive, the signaling process must use thesl_send_confirm() subroutine to return the result of the request to the channel process or custom server. If the primitive fails or is not implemented, report this by using the sl_send_confirm() subroutine to send a confirm primitive with the ReplyCode field set to indicate the failure.