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Understanding Session States

During the FIX session lifetime, state changes occur. the Session class exposes the State property to determine in which state it currently resides.

The following table describes all possible FIX session states that can occur during its lifetime, as well as what a specific state means for a session with a particular role.

StateSession-AcceptorSession-Initiator
DISCONNECTED The session is disconnected. The session is disconnected.
LOGON_IN_PROGRESS The session is waiting for the initial Logon message. The initial Logon message was sent and the session is waiting for the acknowledgment Logon message.
ACTIVE The session is fully established (after the successful Logon exchange). The session is fully established (after the successful Logon exchange).
RECONNECTING N/A (session can't reside in this state). Session is trying to restore the telecommunication link.
LOGOUT_IN_PROGRESS The initial Logout message was sent and the session is waiting for the acknowledgment Logout message. The initial Logout message was sent and the session is waiting for the acknowledgment Logout message.

Tracking Session State Change

Session class exposes StateChangeEvent for its users. Subscribing to this event provides an ability to be notified about all changes in state of particular session.

Example
C#
void OnStateChange(Object sender, StateChangeEventArgs args)
{
    Console.WriteLine(
        "Session {0} changes its state from {1} to {2}.",
        sender, args.PrevState, args.NewState);
}

void run()
{
    Session session = new Session("SenderCompID", "TargetCompID", ProtocolVersion.FIX44);
    session.StateChangeEvent += new Session.StateChangeEventHandler(OnStateChange);
}
VB
Sub OnStateChange(ByVal sender As Object, ByVal args As StateChangeEventArgs)
    Console.WriteLine("Session {0} changes its state from {1} to {2}.", sender, args.PrevState, args.NewState)
End Sub

Sub Run()
    Dim session As New Session("SenderCompID", "TargetCompID", FIXForge.NET.FIX.ProtocolVersion.FIX44)
    AddHandler session.StateChangeEvent, AddressOf OnStateChange
End Sub