RSC/MP 7.2 Programming Manual

Unsolicited Message Service
HP NonStop Remote Server Call (RSC/MP) Programming Manual—522360-004
8-5
Receiving Messages on Workstations
The UMS header information is in the RSCH file on the host system and in the RSC.H
file on the workstation. The header must be included at the beginning of the unsolicited
message. The message consists of a header followed by the data the host is sending.
The host application initializes the header. The workstation application receives the
message data without the header. When calling the WRITEREAD procedure, the host
application receives the header followed by the workstation's reply data (see UMS
Header Description on page 8-7).
The sending process should open the TDP process using the qualifier #RSCUMS. For
example, if the TDP process is $TDPA, then the UMS sender should open
$TDPA.#RSCUMS.
See UMS Host Code Example on page 8-8 for an example of sending an unsolicited
message to a workstation.
Receiving Messages on Workstations
Workstation applications prepare to accept unsolicited messages by registering a
group alias or session alias, using the RscSetOption function, before beginning a
session with the RscBeginSession function. The workstation application then either
requests asynchronous notification or periodically calls the RscUmsCheck function to
retrieve any unsolicited messages. The puIoType parameter returned through the
RscUmsCheck function indicates whether the message was sent from the host system
through either a Guardian WRITE or a WRITEREAD procedure. In the case of a
WRITEREAD, the workstation application must respond to the sender by using the
RscUmsReply function call (see Responding to Messages on page 8-6).
The maximum size of an unsolicited message is 56000 bytes. However, in order to
send a UMS longer than 31000 bytes, the receiving workstation must be configured for
large messages. Attempting to send an unsolicited message longer than 31000
bytes to an improperly configured workstation may result in connection failure.
RscUmsCheck and RscWriteRead function calls can concurrently use the same
RSC/MP session. You can call the RscUmsCheck function while a nowaited I/O is
outstanding.