This document attempts to cover the TDS protocol for:
| TDS Version | Supported Products |
| 4.2 | Sybase SQL Server < 10 and Microsoft SQL Server 6.5 |
| 5.0 | Sybase SQL Server >= 10 |
| 7.0 | Microsoft SQL Server 7.0 |
| 8.0 | Microsoft SQL Server 2000 |
Contents
TDS protocol versions
TDS5 tds version 5.0
TDS7 tds version 7.0
TDS7+ tds version 7.0 and 8.0
TDS5- tds version 5.0 and previous
Variable types used in this document:
CHAR 8-bit char
CHAR[6] string of 6 chars
CHAR[n] variable length string
XCHAR single byte (TDS5-) or ucs2le (TDS7+) characters
INT8 8-bit int
INT16 16-bit int
INT32 32-bit int
UCS2LE Unicode in UCS2LE format
Note: FreeTDS uses TDS_TINYINT for INT8 and TDS_SMALLINT for INT16.
Typical Usage sequences
These are TDS 4.2 and not meant to be 100% correct, but
I thought they might be helpful to get an overall view
of what goes on.
--> Login <-- Login acknowledgement --> INSERT SQL statement <-- Result Set Done --> SELECT SQL statement <-- Column Names <-- Column Info <-- Row Result <-- Row Result <-- Result Set Done --> call stored procedure <-- Column Names <-- Column Info <-- Row Result <-- Row Result <-- Done Inside Process <-- Column Names <-- Column Info <-- Row Result <-- Row Result <-- Done Inside Process <-- Return Status <-- Process Done
The packet format
All packets start with the following 8 byte header.
INT8 INT8 INT16 4 bytes
+----------+-------------+----------+--------------------+
| packet | last packet | packet | unknown |
| type | indicator | size | |
+----------+-------------+----------+--------------------+
Fields:
packet type
0x01 TDS 4.2 or 7.0 query
0x02 TDS 4.2 or 5.0 login packet
0x03 RPC
0x04 responses from server
0x06 cancels
0x07 Used in Bulk
0x0F TDS 5.0 query
0x10 TDS 7.0 login packet
last packet indicator
0x00 if more packets
0x01 if last packet
packet size
(in network byte order)
unknown?
always 0x00
this has something to do with server to server communication/rpc stuff
The remainder of the packet depends on the type of information it is
providing. As noted above, packets break down into the types query, login,
response, and cancels. Response packets are further split into multiple
sub-types denoted by the first byte (a.k.a. the token) following the
above header.
Packet type (first byte) is 2. The numbers on the left are decimal offsets including the 8 byte packet header.
byte var type description
------------------------------
8 CHAR[30] host_name
38 INT8 host_name_length
39 CHAR[30] user_name
69 INT8 user_name_length
70 CHAR[30] password
100 INT8 password_length
101 CHAR[30] host_process
131 INT8 host_process_length
132 ? magic1[6] /* mystery stuff */
138 INT8 bulk_copy
139 ? magic2[9] /* mystery stuff */
148 CHAR[30] app_name
178 INT8 app_name_length
179 CHAR[30] server_name
209 INT8 server_name_length
210 ? magic3[1] /* 0, don't know this one either */
211 INT8 password2_length
212 CHAR[30] password2
242 CHAR[223] magic4
465 INT8 password2_length_plus2
466 INT16 major_version /* TDS version */
468 INT16 minor_version /* TDS version */
470 CHAR library_name[10] /* "Ct-Library" or "DB-Library" */
480 INT8 library_length
481 INT16 major_version2 /* program version */
483 INT16 minor_version2 /* program version */
485 ? magic6[3] /* ? last two octets are 13 and 17 */
/* bdw reports last two as 12 and 16 here */
/* possibly a bitset flag */
488 CHAR[30] language /* e.g. "us-english" */
518 INT8 language_length
519 ? magic7[1] /* mystery stuff */
520 INT16 old_secure /* explanation? */
522 INT8 encrypted /* 1 means encrypted all password fields blank */
523 ? magic8[1] /* no clue... zeros */
524 CHAR sec_spare[9] /* explanation? */
533 CHAR[30] char_set /* e.g. "iso_1" */
563 INT8 char_set_length
564 INT8 magic9[1] /* 1 */
565 CHAR[6] block_size /* in text */
571 INT8 block_size_length
572 ? magic10[25] /* lots of stuff here...no clue */
Any help with the magic numbers would be most appreciated.
byte var type description
---------------------------
0 INT32 total packet size
4 INT[4] TDS Version 0x00000070 for TDS7, 0x01000071 for TDS8
8 INT32 packet size (default 4096)
12 INT8[4] client program version
16 INT32 PID of client
20 INT32 connection id (usually 0)
24 INT8 option flags 1
0x80 enable warning messages if SET LANGUAGE issued
0x40 change to initial database must succeed
0x20 enable warning messages if USE issued
25 INT8 option flags 2
0x80 enable domain login security
0x02 client is an ODBC driver
0x01 change to initial language must succeed
26 INT8 sql type flags (0)
27 INT8 reserved flags (must be 0)
28 INT8[4] time zone (0x88ffffff ???)
32 INT8[4] collation information
36 INT16 position of client hostname (86)
38 INT16 hostname lenght
40 INT16 position of username
42 INT16 username length
44 INT16 position of password
46 INT16 password length
48 INT16 position of app name
50 INT16 app name length
52 INT16 position of server name
54 INT16 server name length
56 INT16 0
58 INT16 0
60 INT16 position of library name
62 INT16 library name length
64 INT16 position of language
66 INT16 language name
(for italian "Italiano" coded UCS2)
68 INT16 position of database name
70 INT16 database name length
72 INT8[6] MAC address of client
78 INT16 position of auth portion
80 INT16 NT authentication length
82 INT16 next position (same of total packet size)
84 INT16 0
86 UCS2LE[n] hostname
UCS2LE[n] username
UCS2LE[n] encrypted password
UCS2LE[n] app name
UCS2LE[n] server name
UCS2LE[n] library name
UCS2LE[n] language name
UCS2LE[n] database name
NT Authentication packet
NT Authentication packet
0 CHAR[8] authentication id "NTLMSSP\0"
8 INT32 1 message type
12 INT32 0xb201 flags
16 INT16 domain length
18 INT16 domain length
20 INT32 domain offset
24 INT16 hostname length
26 INT16 hostname length
28 INT32 hostname offset
32 CHAR[n] hostname
CHAR[n] domain
See documentation on Samba for detail (or search ntlm authentication for IIS)
"current pos" is the starting byte address for a Unicode string within
the packet. The length of that Unicode string immediately follows.
That implies there are at least 2 more strings that could be defined.
(character set??)
Collate structure contain information on characters set encoding and compare method.
INT16 INT16 INT8
+----------+--------+------------+
| codepage | flags | charset_id |
+----------+--------+------------+
codepage windows codepage (see http://www.microsoft.com/globaldev/nlsweb/)
also specified in lcid column of master..syslanguages
flags sort flags
0x100 binary compare
0x080 width insensitive
0x040 Katatype insensitive
0x020 accent insensitive
0x010 case insensitive
If binary flag is specified other flags are not present
Low nibble of flags is a charset specifier (like chinese dialect)
charset_id charset id in master..syscharsets table or zero for no SQL collations
Collations names can be obtained from select name from ::fn_helpcollations()
query
Normal tokens (contained in packets 0xF)
TODOSpecial packets
0x1 1 Language 0x3 3 RPC TDS4.6+
This sample packet contain just SQL commands. It's supported by all TDS version (although TDS5 have others token with similar use)
XCHAR[n] +---------+ | string | +---------+ string SQL text
Do not confuse an RPC packet with an RPC token. The RPC packet is supported by all version of TDS; the RPC token is supported only by TDS 5.0 (and has different format). This is the oldest (and the only one in mssql) way to call directly an RPC. Sybase also documents it, but as 0xE.
INT16 XCHAR[n] INT16
+-------------+----------+-------+----------+
| name length | rpc name | flags | params |
+-------------+----------+-------+----------+
name length length of RPC name in characters.
mssql2k+ support some core RPC using numbers
If a number is used instead of name name length is marked as -1
(null) and a INT16 is used for the name.
0x1 1 sp_cursor
0x2 2 sp_cursoropen
0x3 3 sp_cursorprepare
0x4 4 sp_cursorexecute
0x5 5 sp_cursorprepexec
0x6 6 sp_cursorunprepare
0x7 7 sp_cursorfetch
0x8 8 sp_cursoroption
0x9 9 sp_cursorclose
0xA 10 sp_executesql
0xB 11 sp_prepare
0xC 12 sp_execute ???
0xD 13 sp_prepexec
0xE 14 sp_prepexecrpc
0xF 15 sp_unprepare
rpc name name of RPC.
flags bit flags.
0x1 1 recompile procedure (TDS7+/TDS5)
0x2 2 no metadata (TDS7+)
(I don't know meaning of "no metadata" -- freddy77)
params parameters. See below
Every parameter has the following structure
+-----------+------+ | data info | data | +-----------+------+ data info data information. See below data data. See results for detailData info structure
INT8 XCHAR[n] INT8 INT32
+-------------+------------+-------+-----------------+
| name length | param name | flags | usertype (TDS5) |
+-------------+------------+-------+-----------------+
INT8 varies varies INT8[5] INT8
+------+-------+----------+------------+---------------+
| type | size | optional | collate | locale |
| | (opt) | (opt) | info(TDS8) | length (TDS5) |
+------+-------+----------+------------+---------------+
name length parameter name length (0 if unused)
param name parameter name
flags bit Name Meaning
0x1 TDS_RPC_OUTPUT output parameter
0x2 TDS_RPC_NODEF output parameter has no default value.
Valid only with TDS_RPC_OUTPUT.
usertype usertype
type param type
size see Results
optional see Results. Blobs DO NOT have
optional on input parameters (output blob parameters
are not supported by any version of TDS).
collate info only for type that want collate info and using TDS8
locale length locale information length. Usually 0 (if not locale
information follow, the structure is unknown)
Responses from the server start with a single octet (token) identifying
its type. If variable length, they generally have the length as the second
and third bytes
Tokens encountered thus far:
0x21 33 "Language packet" ? 5.0 only, client-side?
0x71 113 "Logout" 5.0? ct_close(), client-side?
0x79 121 Return Status
0x7C 124 Process ID 4.2 only
0x81 129 7.0 Result 7.0 only
0xA0 160 Column Name 4.2 only
0xA1 161 Column Info --- Row Result 4.2 only
0xA4 164 Table names name of tables in a FOR BROWSE select
0xA5 165 Column info column information in a FOR BROWSE select
0xA7 167 compute related ? Also "control" ?
0xA8 168 Column Info --- Compute Result
0xA9 169 Order By
0xAA 170 Error Message
0xAB 171 Non-error Message
0xAC 172 Output Parameters
0xAD 173 Login Acknowledgement
0xAE 174 "control" ?
0xD1 209 Data --- Row Result
0xD3 211 Data --- Compute Result
0xD7 215 "param packet" ? **bdw**
0xE2 226 Capability packet information on server
0xE3 227 Environment Change (database change, packet size, etc...)
0xE5 229 Extended Error Message
0xE6 230 "DBRPC" ? 5.0 only RPC calls
0xEC 236 "param format packet" ?
0xEE 238 Result Set
0xFD 253 Result Set Done
0xFE 254 Process Done
0xFF 255 Done inside Process
"Language" (0x21 33)
int? INT8 CHAR[n]
+--------+--------+--------+
| length | status | string |
+--------+--------+--------+
"Logout" (0x71 113)
No information. (1 byte, value=0 ?)
Return Status (0x79 121)
4 bytes
+---------------+
| Return status |
+---------------+
The return value of a stored procedure.
Process ID (0x7C 124)
8 bytes
+----------------+
| process number |
+----------------+
Presumably the process ID number for an executing stored procedure.
(I'm not sure how this would ever be used by a client. *mjs*)
Result - TDS 7.0+ (0x81 129)
INT16
+----------+-------------+
| #columns | column_info |
+----------+-------------+
The TDS 7.0 column_info is formatted as follows for each column:
INT16 INT16 INT8 varies varies INT8[5] INT8 UCS2LE[n]
+----------+-------+------+-------+----------+------------+-------------+---------+
| usertype | flags | type | size | optional | collate | name length | name |
| | | | (opt) | (opt) | info(TDS8) | | |
+----------+-------+------+-------+----------+------------+-------------+---------+
usertype type modifier
flags bit flags
0x1 can be NULL
0x8 can be written (it's not an expression)
0x10 identity
type data type, values >128 indicate a large type
size none for fixed size types
4 bytes for blob and text
2 bytes for large types
1 byte for all others
optional
INT8 INT8
+-----------+-------+
numeric/decimal types: | precision | scale |
+-----------+-------+
INT16 UCS2LE[n]
+-------------------+------------+
blob/text types: | table name length | table name |
+-------------------+------------+
collate info are available only using TDS8 and for characters types (but not
for old type like short VARCHAR, only 2byte length versions)
Column Name (0xA0 160)
INT16 INT8 CHAR[n] INT8 CHAR[n]
+--------------+---------+--------------+------+---------+--------------+
| total length | length1 | column1 name | .... | lengthN | columnN name |
+--------------+---------+--------------+------+---------+--------------+
Column Info - Row Result (0xA1 161)
Column Info - Compute Result (0xA8 168)
INT8 CHAR[n] INT8 INT16 INT16 INT16
+-------------+--------------+---------+---------+---------+---------+
| column name | column name | unknown | user | unknown | column |
| length | | | type | | type |
+-------------+--------------+---------+---------+---------+---------+
INT8 INT8 INT8 INT8 CHAR[n] 1 byte
+-------------+----------+----------+----------+------------+----------+
| column size |precision | scale | t length | table name | unknown |
| (optional) |(optional)|(optional)|(optional)| (optional) | |
+-------------+----------+----------+----------+------------+----------+
column name length
column name column name in result set, not necessarily db column name
unknown unknown (0, 16 ?)
user type usertype column from syscolumns
unknown always 0's
column type (need an appendix for discussion of column types)
column size not present for fixed size columns
precision present only for SYBDECIMAL and SYBNUMERIC
scale present only for SYBDECIMAL and SYBNUMERIC
t length present only for SYBTEXT and SYBIMAGE, length of table name
table name present only for SYBTEXT and SYBIMAGE
unknown always 0x00
"tabname" (0xA4 164)
"col info" (0xA5 165)
compute "control" ? (0xA7 167)
"control" (0xAE 174)
Miscellaneous note (from *bdw* ?) found with 0xAE:
has one byte for each column,
comes between result(238) and first row(209),
I believe computed column info is stored here, need to investigate
Order By (0xA9 169)
INT16 variable (1 byte per col)
+--------+---------+
| length | orders |
+--------+---------+
length Length of packet(and number of cols)
orders one byte per order by indicating the
column # in the output matching the
order from Column Info and Column Names
and data in following Row Data items.
A 0 indicates the column is not in the
resulting rows.
an example:
select first_name, last_name, number from employee
order by salary, number
assuming the columns are returned in the order
queried:
first_name then last_name, then number. we would have:
----------------
| 2 | 0 | 3 |
----------------
where length = 2 then the orders evaluate:
0 for salary, meaning there is no salary data returned
3 for number, meaning the 3rd data item corresponding
to a column is the number
Error Message (0xAA 170)
Non-error Message (0xAB 171)
Extended Error Message (0xE5 229)
INT16 4 bytes INT8 INT8
+--------+------------+-------+-------+
| length | msg number | state | level |
+--------+------------+-------+-------+
INT16 CHAR[n] INT8 CHAR[n] INT8 CHAR[n] INT16
+----------+---------+----------+---------+----------+---------+-------+
| m length | message | s length | server | p length | process | line# |
+----------+---------+----------+---------+----------+---------+-------+
length Length of packet
msg number SQL message number
state ?
level An error if level > 10, a message if level <= 10
m length Length of message
message Text of error/message
s length Length of server name
server Name of "server" ?
p length Length of process name
process name Stored procedure name, if any
line# Line number of input which generated the message
Output Parameters (0xAC 172)
Output parameters of a stored procedure.
INT16 INT8 CHAR[n] 5 bytes INT8
+--------+----------+---------+---------+----------+------+
| length | c length | colname | unknown | datatype | .... |
+--------+----------+---------+---------+----------+------+
length Length of packet
c length Length of colname
colname Name of column
datatype Type of data returned
The trailing information depends on whether the datatype is
a fixed size datatype.
N bytes
+---------+
Datatype of fixed size N | data |
+---------+
INT8 INT8 N bytes
+-------------+---------------+--------+
Otherwise | column size | actual size N | data |
+-------------+---------------+--------+
Login Acknowledgement (0xAD 173)
INT16 INT8 4 bytes INT8 CHAR[n] 4 bytes
+--------+-------+---------+----------+--------+----------+
| length | ack | version | t length | text | ser_ver |
+--------+-------+---------+----------+--------+----------+
length length of packet
ack 0x01 success 4.2
0x05 success 5.0
0x06 failure 5.0
version TDS version 4 bytes: major.minor.?.?
t length length of text
text server name (ie 'Microsoft SQL Server')
For TDS7+ this is in ucs2 format
ser_ver Server version
(with strange encoding, differring from TDS version)
Data - Row Result (0xD1 209)
Data - Compute Result (0xD3 211)
INT8 variable size
+----------+--------------------+
| token | row data |
+----------+--------------------+
Row data starts with one byte (decimal 209), for variable length types,
a one byte length field precedes the data, for fixed length records just
the data appears.
Note: nullable integers and floats are variable length.
For example: sp_who
The first field is spid, a smallint
The second field is status a char(12), in our example "recv sleep "
The row would look like this:
byte 0 is the token
bytes 1-2 are a smallint in low-endian
byte 3 is the length of the char field
bytes 4-15 is the char field
byte 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
hex D1 01 00 0C 72 65 63 76 20 73 6C 65 65 70 20 20
209 1 0 12 r e c v ' ' s l e e p ' ' ' '
Parameter packet (0xD7 215)
No information
Capability packet (0xE2 226)
INT16 variable
+--------+--------------+
| length | capabilities |
+--------+--------------+
length Length of capability string
capabilities Server capabilities? Related to login magic?
Environment change (0xE3 227)
INT16 INT8 INT8 CHAR[n] INT8 CHAR[n]
+--------+----------+-----------+---------+-----------+---------+
| length | env code | t1 length | text1 | t2 length | text2 |
+--------+----------+-----------+---------+-----------+---------+
env code Code for what part of environment changed
0x01 database context
0x02 language
0x03 character set
0x04 packet size
0x05 TDS7+ LCID
0x06 TDS7+ ??? (sort method? sql server encoding?)
0x07 Collation info
text1 Old value
text2 New value
text1 and text2 are text information (coded in ucs2 in TDS7+) except
collation info that's a structure (see collation structure)
DB RPC ? (0xE6 230)
No information.
Param format (sent by client?) (0xEC 236)
INT16 INT16 variable size
+---------+------------+-------------------+
| length | number of | parameter info |
| | parameters | |
+---------+------------+-------------------+
length length of message following this field
number of parameters number of parameter formats following
list of formats I (*bdw*) imagine it uses the column format structure.
Result Set (0xEE 238)
INT16 INT16 variable size
+---------+------------+-----------------+
| length | number of | column info |
| | columns | |
+---------+------------+-----------------+
Fields:
length length of message following this field
number of columns number of columns in the result set, this many column
information fields will follow.
column info column info
Result Set Done (0xFD 253)
Process Done (0xFE 254)
Done Inside Process (0xFF 255)
INT16 INT16 INT32
+-----------+---------+-----------+
| bit flags | unknown | row count |
+-----------+---------+-----------+
Fields:
bit flags 0x01 more results
0x02 error (like invalid sql syntax)
0x10 row count is valid
0x20 cancelled
unknown 2,0 /* something to do with block size perhaps */
row count number of rows affected / returned in the result set.
(FIXME check if "affected / returned" is correct)
"Result Set Complete" is the end of a query that doesn't create a process
on the server. I.e., it doesn't call a stored procedure.
"Process Done" is the end of a stored procedure
"Done In Process" means that a query internal to a stored procedure
has finished, but the stored procedure isn't done overall.
Acknowledgements
The following people have contributed to this document:
Brian Bruns (first draft, protocol discovery)
Brian Wheeler (protocol discovery)
Mark Schaal (second draft)
Frediano Ziglio
(short list)