Envoy Application Programming Manual

BISYNC Point-To-Point Protocol
Envoy Application Programming Manual—427159-001
3-29
WRITEREAD Procedure (Limited Conversational
Exchange)
WRITEREAD Procedure (Multileaving Conversational Exchange)
The WRITEREAD procedure causes Envoy, on behalf of the application process, to
send the message in the buffer of the application process to the remote station. A call to
WRITEREAD completes (Example 3-12
) when the remote station returns a message to
this buffer.
The successful transmission of a message is indicated by a condition code of CCE upon
completion of the WRITEREAD. If a message is returned, the count read parameter is
greater than zero.
In multileaving conversational mode, DLE ACK0, NAK, EOT, and SOH ENQ are
treated as text characters, not control characters. Therefore, an application process can
send these control sequences as text. The other control characters (RVI, ETX) cause a
format error, and the erroneous text is returned to the application process.
The file-system errors shown in Table 3-14
can occur on a multileaving conversational
WRITEREAD.
Example 3-11. WRITEREAD Procedure (ID Exchange by Called Station)
Local Remote
line state = CONTROL
CALL WRITEREAD(...)
| ID ACK0
| <-- message or
| EOT
(WRITEREAD completes)
error = 0
line state = READ
if message received
or
line state = CONTROL
if EOT received
Example 3-12. WRITEREAD Procedure (Multileaving Conversational Exchange)
Local Remote
line state = CONVERSATIONAL
CALL WRITEREAD(...)
| message -->
| <-- DLE ACK0 or
| message
(WRITE completes)
error = 0
line state = CONVERSATIONAL