FIX Protocol Message 35=A: Logon

First message of a FIX session. The initiator sends it to authenticate and to set session parameters such as HeartBtInt (108) and EncryptMethod (98); the acceptor replies with its own Logon.

MsgType (tag 35): A
FIX name: Logon
Category: Session (administrative)
FIX versions: FIX 4.0 to 4.4 and FIXT 1.1

Logon in each FIX version

The full field layout as defined in a specific version.

Required fields

Body fields that every Logon message must carry in FIX 4.4, in addition to the standard header and trailer.

98EncryptMethod
108HeartBtInt

Field layout

All body fields in the order of the FIX 4.4 definition, with components and repeating groups indented. A field inside an optional component or group is required only when that component or group is present.

Tag	Field	Required
98	EncryptMethod	Required
108	HeartBtInt	Required
95	RawDataLength	Optional
96	RawData	Optional
141	ResetSeqNumFlag	Optional
789	NextExpectedMsgSeqNum	Optional
383	MaxMessageSize	Optional
384	NoMsgTypes (repeating group)	Optional
372	RefMsgType	Optional
385	MsgDirection	Optional
464	TestMessageIndicator	Optional
553	Username	Optional
554	Password	Optional

Standard header and trailer

Every FIX message starts with the standard header, whose required fields are BeginString (8), BodyLength (9), MsgType (35), SenderCompID (49), TargetCompID (56), MsgSeqNum (34) and SendingTime (52), and ends with the trailer field CheckSum (10).

Decode a Logon message

All FIX message types · All FIX tags

Field and message data comes from the QuickFIX data dictionaries for FIX 4.0 to 5.0 SP2 and FIXT 1.1, used under the QuickFIX Software License. This product includes software developed by quickfixengine.org (http://www.quickfixengine.org/). Enumerated value names are converted to plain text for reading.