HP-UX SNAplus2 MS Programmer's Guide

Writing MS Applications
Description of the MS API Entry Points
Chapter 240
Using the Callback Routine for Indications
The callback routine supplied with the REGISTER_MS_APPLICATION
VCB can receive the following indications:
• FP_NOTIFICATION (if the application requested this information
when registering)
• MDS_MU_RECEIVED
• MS_STATUS
The callback routine supplied with the
REGISTER_NMVT_APPLICATION VCB can receive the following
indications:
• NMVT_RECEIVED (if the application did not request conversion
from NMVT-level data to MDS-level data)
• MDS_MU_RECEIVED (if the application requested conversion from
NMVT-level data to MDS-level data)
• MS_STATUS
Although the application allocates the VCBs for MS verbs, SNAplus2
allocates the VCBs for indications. Therefore, the application has access
to the VCB information only from within the callback routine; the VCB
pointer that SNAplus2 supplies to the callback routine is not valid
outside the callback routine. The application must either complete all the
required processing from within the callback routine, or it must make a
copy of any VCB data that it needs to use outside this routine.
In the event that the MS application needs to make a copy of the data
supplied on the callback routine and the MS application is using a
signal-based scheduling mode, an operating system limitation may
prohibit memory allocation. In this case, some memory must be
preallocated before the REGISTER_MS_APPLICATION or
REGISTER_NMVT_APPLICATION verb is issued. For more information
about signal-based scheduling mode, see “Signal-Based Scheduling
Mode”.
Processing of indications in the callback routine must fulfill the following
additional requirements:
• If an NMVT-level application uses
REGISTER_NMVT_APPLICATION to receive incoming NMVTs, it
must be capable of receiving a data length of 512 bytes (the
maximum NMVT size).