Envoy Application Programming Manual
Table Of Contents
- What’s New in This Manual
- About This Manual
- 1 Application Programming With Envoy
- 7 ADM-2 Multipoint Supervisor Protocol
- 8 TINET Multipoint Supervisor Protocol
- 9 Burroughs Point-To-Point Protocol
- 10 Asynchronous Line Supervisor Protocol
- A ASCII Character Set
- B ASCII to EBCDIC Code Conversion
- C File-System Procedures
- D Statistics Messages
- E S-Series Changes to Envoy
- NonStop™ Himalaya S-Series Server Architecture
- G-Series Migration Considerations
- CBSENSEON and CFSENSEON Modifiers
- LEOTRESYN and NOLEOTRESYN Modifiers
- Treatment of Characters After the Termination Character
- Number of SYN Characters
- DTR Drop
- Reporting of Parity Error
- Half-Duplex Support for Asynchronous Lines
- Controller Replacement
- SYSGEN and COUP
- Unit Numbers
- FDX Line Changes
- No Support for Auto-Call Unit
- Glossary
- Index
Burroughs Point-To-Point Protocol
Envoy Application Programming Manual—427159-001
9-2
Application Process Interface
Application Process Interface
An application process acting as a station in a Burroughs point-to-point network
interacts with Envoy and the remote station by way of Guardian 90 file-system
procedure calls.
This subsection includes:
•
Opening a Line on page 9-2
•
Line Contention on page 9-3
•
Retries on page 9-3
•
Timeouts on page 9-3
Opening a Line
Before it can transmit or receive data, the application process must first open a
communications line. The line must be opened for exclusive read-write access. Only the
application process (and its backup) can open the line.
To send a message, the application process calls the file-system WRITE procedure.
When the local station is in either the CONTROL state or READ state, the first call to
the WRITE procedure causes Envoy to bid for the line and then, after the bid is
accepted, send the message. Subsequent calls to the WRITE procedure send messages
but do not cause a bid for the line.
To receive a message, the application process calls the READ procedure. Envoy returns
a positive acknowledgment to a line bid and accepts the first message from the sender.
Subsequent calls to the READ procedure accept subsequent messages. With each call to
the READ procedure, Envoy acknowledges the preceding message, accepts the current
message, and makes the received data available to the application process.
After sending one or more messages, the sender indicates the end of transmission and
gives up master status by sending an end-of-transmission (EOT) character to the
receiver. After the EOT is sent, either station may bid for the line. The application
process sends the EOT sequence in either of two ways:
•
Calling the READ procedure following a WRITE to monitor the line for a line bid
from the other station
•
Calling the CONTROL procedure to simply send an EOT
Both the error indication returned from the call to the READ procedure (condition code
CCL) and file-system error 163 (EOT received) returned from a call to the FILEINFO
procedure indicate the end of transmission to the receiver.