2.2.3.1.1 Type

Type defines the type of message. Type is a 1-byte unsigned char. The following table describes the types that are available.

Value	Description	Packet contains data?
1	SQL batch	Yes
2	Pre-TDS7 Login<5>	Yes
3	RPC	Yes
4	Tabular result	Yes
5	Unused
6	Attention signal	No
7	Bulk load data	Yes
8	Federated Authentication Token	Yes
9-13	Unused
14	Transaction manager request	Yes
15	Unused
16	TDS7 Login<6>	Yes
17	SSPI	Yes
18	Pre-Login	Yes

If an unknown Type is specified, the message receiver SHOULD disconnect the connection. If a valid Type is specified, but is unexpected (per section 3), the message receiver SHOULD disconnect the connection. This applies to both the client and the server. For example, the server could disconnect the connection if the server receives a message with Type equal 16 when the connection is already logged in.

The following table highlights which messages, as described previously in sections 2.2.1 and 2.2.2, correspond to which packet header type.

Message type	Client or server message	Packet header type
Pre-Login	Client	18
Login	Client	16 + 17 (if Integrated authentication)
Federated Authentication Token	Client	8
SQL Batch	Client	1
Bulk Load	Client	7
RPC	Client	3
Attention	Client	6
Transaction Manager Request	Client	14
FeatureExtAck	Server	4
Pre-Login Response	Server	4
Login Response	Server	4
Federated Authentication Information	Server	4
Row Data	Server	4
Return Status	Server	4
Return Parameters	Server	4
Response Completion	Server	4
Session State	Server	4
Error and Info	Server	4
Attention Acknowledgement	Server	4