HP X.25/9000 Programmer's Guide

74 Chapter5
Receiving and Transmitting Out-of-band Information
Building a Signal Handler
CAUTION If the out-of-band data is not read quickly, the out-of-band data
queue could overflow. If the queue overflows, subsequent
out-of-band events are discarded.
Out-of-band Events
There are eight out-of-band (OOB) events which a signal handler can
receive. The out-of-band values are defined in x25.h. The out-of-band
values are:
• OOB_INTERRUPT
• OOB_VC_CLEAR
• OOB_VC_DBIT_CONF
• OOB_VC_INTERRUPT_CONF
• OOB_VC_L2DOWN
• OOB_VC_MSG_TOO_BIG
• OOB_VC_RESET
• OOB_VC_RESET_CONF
The out-of-band events are described below.
OOB_INTERRUPT
An INTERRUPT packet was received. The confirmation is sent by the
subsystem when reading this event if the MSG_PEEK flag was not set.
The buffer received can contain 3 to 34 bytes of data, the first 2 bytes of
which are its length and the event code respectively. The remainder of
the buffer contains the interrupt data. How the interrupt data is used is
application-dependent.
NOTE The maximum number of bytes of interrupt data depends on the version
of X.25 recommendations being used by the network. The 1980 X.25
recommendations permit 1 byte of interrupt data while the 1984 X.25
recommendations permit up to 32 bytes of interrupt data.
36960-90061.bk Page 74 Friday, November 10, 2000 3:42 PM