Structure | Related Messages

The Logon <A> message is utilized to authenticate a user attempting to establish a connection to a remote system. The Logon <A> message must be the first message sent by the application requesting to initiate a FIX session.

The HeartBtInt <108> (108) field is used to declare the timeout interval for generating heartbeats.

Upon receipt of a Logon <A> message the session acceptor will authenticate the party requesting connection and issue a Logon <A> message as acknowledgment that the connection request has been accepted. The acknowledgment Logon <A> can also be used by the initiator to validate that the connection was established with the correct party.

The session acceptor must be prepared to immediately begin processing messages after receipt of the Logon <A>. The session initiator can choose to begin transmission of FIX messages before receipt of the confirmation Logon <A>, however it is recommended that normal message delivery wait until after the return Logon <A> is received to accommodate encryption key negotiation.

The confirmation Logon <A> can be used for encryption key negotiation. If a session key is deemed to be weak, a stronger session key can be suggested by returning a Logon <A> message with a new key. This is only valid for encryption protocols that allow for key negotiation. (See the FIX Home Page Application notes for more information on a method for encryption and key passing.)

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