Envoy Application Programming Manual

BISYNC Multipoint Tributary Protocol
Envoy Application Programming Manual—427159-001
5-24
READ Procedure
Initial READ (Line in WRITE State)
An initial READ while the line is in the WRITE state (that is, a tributary station is
transmitting), causes Envoy, on behalf of the application process, to send an EOT
sequence to the remote station (Example 5-6). Sending EOT is the normal method for
terminating a transmission to the supervisor station. Following the transmission of the
EOT sequence, the action taken is the same as that for an initial READ from the
CONTROL state (that is, Envoy again monitors the line for polling and selection
sequences).
The file-system errors that apply to an initial READ from the CONTROL state also
apply to an initial READ from the WRITE state.
Table 5-10. Continuation READ File-System Errors
Error State Description Resultant Line Number
0 No error. The message is returned to applica-
tion process’s buffer.
READ
60 Request is invalid for line state. unknown
161 Impossible event occurred for line state. unknown
162 Operation timed out. The acknowledgment was
sent but no message was received within the
timeout or retry limits.
CONTROL
172 Reply not proper for protocol. The data
received while waiting for a message was not
proper for the BISYNC protocol.
CONTROL
173 Transmission error. The message received was
in error and a NAK sequence has been sent the
number of times specified by the retry value.
CONTROL
177 Text overrun. The length of the message
received exceeds the length specified in the
read count parameter. The READ has been
attempted the number of times specified by the
retry value.
CONTROL
178 No address list has been specified. CONTROL
Example 5-6. Initial READ (Line in WRITE State)
Supervisor (Local) Tributary (Remote)
line state = WRITE
CALL READ(...)
| EOT -->
|
v