HDLC-Frame Protocol User's Guide (February 2004)

Using HDLC.FRAME Protocol
Status and Error Messages
Chapter 322
Status and Error Messages
Error conditions and important events are reported to the application
program through three kinds of status codes. These are “Transmit
completion”, “Unsolicited” and “Receive completion” status codes.
The defines for these status codes are located in
/usr/include/zcomstatus.h and /usr/include/zx25status.h.
Transmit Completion Status Codes
Transmit completion status is generated by the protocol on all transmit
messages. Depending on the mode parameter selected when using the
zsend call, the application will see either No transmit response
messages, Error responses only, or All transmit response messages. The
status code contained in the header of these messages indicates either
the successful transmission of the message, or the reason why it could
not be transmitted.