Table of Contents

STANDARD HEADER

STANDARD HEADER

The Standard Header precedes all FIX messages and provides session identification, message routing, and sequencing information.

Core Components

Message Identity: BeginString (8), MsgType (35), BodyLength (9)
Session Identity: SenderCompID (49), TargetCompID (56)
Sequencing: MsgSeqNum (34), SendingTime (52)
Authentication: SecureData (91), SecureDataLen (90) - Logon only

Message Specification

Required in all messages

Tag	Field Name	Type	Req'd	Description
8	BeginString	String	Y	Always “FIX.4.2”
9	BodyLength	Int	Y	Message length (excluding 8, 9, 10)
35	MsgType	String	Y	Message type identifier
34	MsgSeqNum	Int	Y	Message sequence number
49	SenderCompID	String	Y	Sender identifier
56	TargetCompID	String	Y	Target identifier
52	SendingTime	UTCTimestamp	Y	Message transmission time
43	PossDupFlag	Boolean	O	Y=Possible duplicate
97	PossResend	Boolean	O	Y=Possible resend
50	SenderSubID	String	C	Trader name (Multi-Trader mode)
57	TargetSubID	String	O	Target trader name
122	OrigSendingTime	UTCTimestamp	C	Original time (resends only)
369	LastMsgSeqNumProcessed	Int	O	Last received sequence
90	SecureDataLen	Int	C	License code length (Logon only)
91	SecureData	String	C	License code (Logon only)

Direction Rules

Inbound (Client → T4):

SenderCompID (49) = T4 Application Name
TargetCompID (56) = T4 Firm Name

Outbound (T4 → Client):

SenderCompID (49) = T4 Firm Name
TargetCompID (56) = T4 Application Name

Notes

First three tags must be: 8, 9, 35
Multi-Trader mode requires SenderSubID (50) for order messages
SecureData/SecureDataLen used only in Logon
Times in UTC format: YYYYMMDD-HH:MM:SS.sss