Envoy Application Programming Manual

BISYNC Point-To-Point Protocol
Envoy Application Programming Manual—427159-001
3-12
Normal Text
Messages must be formatted according to BISYNC rules. Prior to transmitting a
message, the application process must place the specific BISYNC control characters for
a particular message type (such as, heading, text, transparent text, and so on) in the
message. When a message is received, the control characters are returned in the data to
indicate the type of message received. Note that after a message is received in the
application’s buffer, it does not contain control-generated SYN characters, inserted DLE
characters (for transparent text), or block-check characters.
The BISYNC point-to-point protocol supports the following message formats:
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Normal Text on page 3-12
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Transparent Text on page 3-12
•
Headings on page 3-13
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Intermediate Text Blocking on page 3-13
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ID Exchange on page 3-15
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BCC Calculation on page 3-15
Normal Text
Normal text is indicated by messages having the following form:
message = STX—text—ETB
message = STX—text—ETX
(message length = 2 + text length)
Transparent Text
Transparent text is indicated by messages having the following form:
message = DLE STX—text—ETB
message = DLE STX—text—ETX
(message length = 3 + text length)
The application process initiates transparent mode by inserting a DLE control character
before the STX. Transparent text, including data link control characters, continues to be
sent until a terminating ETB or ETX is received.
The transmission of DLE text characters is handled entirely by Envoy hardware and does
not apply to the SWIFT protocol. Envoy automatically inserts the DLE character in front
of the DLE text character upon transmission and deletes the DLE character in front of
the DLE text character upon reception. The application process deals only with the
original binary text.