General comments

• The SYBSET protocol is transmitted as the data of an ACNET packet.  SYBSET protocol structures use the ACNET network representation.
• The setdat process on each front-end is responsible for forwarding settings to SYBSET. Setdat connects to ACNET with the rad-50 handle WRITER for this purpose. SYBSET runs on CDBS(X) and connects to ACNET with the rad-50 handle "DBM...".
• In the description of the packet formats below all fields in the packets abut.

WRITER forwarded settings list packet

 

Length(bytes)	Field Description	Type
1	Typecode	1-byte unsigned integer
1	Filler/Reserved	1-byte unsigned integer
2	Maximum expected length(bytes) of reply	2-byte unsigned integer
2	Number of entries in list	2-byte unsigned integer
not fixed	Forwarded settings structure 1	structure see below
---	---	---
not fixed	Forwarded settings structure N	structure see below

 
•  The typecode is always 1.  The filler is always 0.
• Remeber that due to ACNET network representation the typecode and filler will be swapped on the wire.

Forwarded settings structure

 

Length(bytes)	Field Description	Type
1	Console number	1-byte unsigned integer
4 bits	Modifier	4-bit unsigned integer
4 bits	Function	4-bit unsigned integer
4	Property-device index pair	4-byte unsigned integer
2	Number of bytes requested from property data (ILEN)	2-byte unsigned integer
2	Offset in bytes to requested property data (usually)	2-byte unsigned integer
ILEN + ILEN mod 2	Setting data	unknown to WRITER and SYBSET

 
• Console number is always 0.  Modifier is always 0.  Function is always 3.
• Remember due to ACNET network representation the console number and modifier-function will be swapped on the wire.
• The property index in a property-device index pair is placed in the most-significant byte of the integer.
• The device index in a property-device index pair is contained in the least-significant 20 bits.  The most-significant 4 bits may be used for flags of various sorts.
• Please refer to the  Property Notes  for information about property indices and there meanings.
• The ILEN mod 2 term in the length of the data insures that everything is word aligned.  The data in the packet should be left-justified, i.e., should be in the bytes with the lowest offsets from the start of the packet.   However, since the data in the packet is in network representation the data will not be left-justified on the wire.   On the wire the data will be word-wise byte-swapped, which causes among other things the padding byte to be the next to last byte on the wire.   Note that Charlie's Acnet implementation does not perform the word-wise byte-swap so the user's methods must use the network represenation justification when assigning values to the memory area passed to the method by MOOC.

SYBSET/DBM... forwarded settings reply packet

 

Length(bytes)	Field Description	Type
2	Error status for forwarded setting 1	2-byte signed integer
2	Data-pointer for forwarded setting 1	unknown to WRITER and SYBSET
---	---	---
2	Error status for forwarded setting N	2-byte signed integer
2	Data-pointer for forwarded setting N	unknown to WRITER and SYBSET

 
• The error status contains an error byte and a facility byte.  The facility byte is an unsigned 1-byte integer.  The error byte is a signed 1-byte integer.  The error byte is in the most-significant byte of the error status.   A zero error status indicates success.  A negative error indicates failure, a positive error indicates partial success, e.g., a pending.   The facility indicates what returned the error.
• Currently SYBSET always returns DBM_NODATA (facility = 16(DBM), error = 2) for the error statuses.  Since no data is expected for forwarded setting requests this error status indicates success.
• The data-pointers are always zero since no data is returned by a forwarded setting requests.

Other Comments

• This protcol contains unused/fixed fields, because this protocol used to support other functionality in the pre-Sybase era.  The full pre-Sybase version of this protocol is described in section 5.3 of design note 22.