Envoy Application Programming Manual

BISYNC Multipoint Tributary Protocol
Envoy Application Programming Manual—427159-001
5-2
Application Process Interface
Application Process Interface
An application process acting as a tributary station in a multipoint network interacts with
Envoy and the supervisor station using Guardian 90 file-system procedure calls.
This subsection includes:
•
Opening a Line on page 5-2
•
Station Addresses on page 5-2
•
ASCII and EBCDIC Line Code on page 5-6
•
Retries on page 5-6
•
Timeouts on page 5-7
•
Limited Conversational Mode on page 5-7
Opening a Line
Before it can transmit or receive data, the application process must first open a
communications line. BISYNC multipoint lines are always opened for exclusive read-
write access. The backup process of the application also can open the line.
Station Addresses
A single application process can act as one or more multipoint tributary stations. The
station addresses, which an application process represents, must be passed to Envoy in
the form of an address list. The address list consists of the poll addresses of any tributary
stations that the application process represents, followed by the select addresses of those
stations. The application process passes the address list to Envoy by calling the
DEFINELIST procedure.
The format of the address list is described under Address-List Format
on page 5-11. The
application process must indicate to Envoy whether a particular station has data to send
or is able to be selected. The application process indicates that a station has data to send
by making its poll state active; it indicates that a station can accept data by making its
Table 5-1. BISYNC Multipoint Tributary Formats
BISYNC Multipoint Tributary Format
heading SOH-head-ETB BCC
heading-text SOH-head-STX-text-ETB|ETX BCC
text STX-text-ETB|ETX BCC
transparent text DLE STX-text-ETB|ETX BCC or SOH-head-DLE STX-
text-ETB|ETX BCC
intermediate blocked text STX-text-ITB BCC-text-ETX BCC or DLE STX-text-
ITB BCC-text-ETX BCC