Q130593: Interpreting SNA Server API Traces: Byte Packing Considerations
Article: Q130593
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.0,2.1,2.11,2.11 SP1,2.11 SP2,3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
Operating System(s):
Keyword(s): kbnetwork kbsna211sp1 kbsna211sp2 kbsna300sp1 kbsna300sp2 kbsna300sp3 sna4 kbsna400sp1
Last Modified: 12-JUN-2001
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The information in this article applies to:
- Microsoft SNA Server, versions 2.0, 2.1, 2.11, 2.11 SP1, 2.11 SP2, 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1
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SUMMARY
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When interpreting Verb Control Blocks (VCB) within SNA Server API traces, the
interpreter must consider the packing alignment of each structure. The packing
depends on the #include file used to build the application. The standard SNA API
include files shipped with SNA Server perform the packing of the VCB depending
on whether the program is built using Win16 or Win32.
MORE INFORMATION
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Sample VCB STRUCTURE for TP_STARTED APPC API verb:
TP_STARTED
opcode unsigned short int (WORD (2 Bytes))
opext unsigned char (BYTE)
reserv2 unsigned char (BYTE)
primary_rc unsigned short int (WORD (2 Bytes))
secondary_rc unsigned long int (DWORD (4 Bytes))
lu_alias unsigned char[8] (8 bytes)
tp_id unsigned char[8] (8 bytes)
tp_name unsigned char[64] (64 bytes)
WIN32
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With Windows NT (32-bit) compilations, VCBs are not packed. As a result, both
DWORDs and WORDs begin on WORD boundaries, and BYTEs begin on BYTE boundaries.
The following is an excerpt from a trace taken on an SNA Server using a Win32
APPC application:
TP_STARTED response, result = PARAMETER_CHECK
Type:Sync VerbID:00001800
---- Verb Parameter Block at address 0014CBC0 ----
14000000 00010000 00000003 53444653 <............SDFS>
44462020 00000000 F0DE1400 D9E4D4C2 <DF ....0...RUMB>
C1F4F0F0 00000000 00000000 00000000 <A400............>
00000000 00000000 00000000 00000000 <................>
00000000 00000000 00000000 00000000 <................>
00000000 00000000 00000000 <............ >
Referring to the "VCB STRUCTURE for TP_STARTED APPC API verb" above,
the verb control block parameters are decoded as follows for Win32:
opcode = 1400
opext = 00
reserv2 = 00
primary_rc = 0001 (the subsequent two bytes "0000" are ignored)
secondary_rc = 00000003
lu_alias = 53 44 46 53 44 46 20 20 ("SDFSDF ")
tp_id = 00 00 00 00 F0 DE 14 00
tp_name = D9 E4 D4 C2 C1 F4 F0 F0 ("RUMBA400 <nulls>")
...
WIN16
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With Windows 3.x (16-bit) compilations, VCBs are also not packed, but are aligned
differently than Windows NT (32-bit) compilations. With Win16, DWORDs and WORDs
start on WORD boundaries, and BYTEs are on BYTE boundaries.
The following is an excerpt from a trace taken on a Windows for Workgroups client
using a Win16 APPC application:
...
TP_STARTED response, result = PARAMETER_CHECK
Type:Sync VerbID:0000180F
---- Verb Parameter Block at address 300F:0000 ----
14000000 00010000 00035344 46202020 <..........SDF >
20200F00 01004B16 DF22D9E4 D4C2C1F4 < ....K.."RUMBA4>
F0F00000 00000000 00000000 00000000 <00..............>
00000000 00000000 00000000 00000000 <................>
00000000 00000000 00000000 00000000 <................>
00000000 00000000 0000 <.......... >
...
For Win16, note that the secondary return code immediately follows the primary
return code (omitting the two NULL bytes which separate these fields in the
Win32 trace above).
Additional query words: prodsna
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Keywords : kbnetwork kbsna211sp1 kbsna211sp2 kbsna300sp1 kbsna300sp2 kbsna300sp3 sna4 kbsna400sp1
Technology : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ200 kbSNAServ211 kbSNAServ400 kbSNAServ210 kbSNAServ211SP1 kbSNAServ211SP2 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ300SP2
Version : WINDOWS:2.0,2.1,2.11,2.11 SP1,2.11 SP2,3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
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