Hi,
I assume this has more or less historic reasons. It is done the same way in the C++ implementation.
The C# implementation also does not validate seqnums on reception of a Logout message.
Another way to ensure that the seqnums are in sync is to send a TestRequest before Logout. That will
trigger a Resend if seqnums are not in sync. Of course, this does only work when your side initiates
the Logout.
Cheers,
Chris.
On 19.09.19 18:20, Oleg Smirnov wrote:
> QuickFIX/J Documentation:http://www.quickfixj.org/documentation/
> QuickFIX/J Support:http://www.quickfixj.org/support/
>
>
>
> Hello,
>
> Could you please answer the question:
> */Why the QuickFIX/J library doesn't validate MsgSeqNum when it receives a Logout message?/*
>
> It's very strange because according to *Page 13* of the FIX Transport protocol specification
> <https://www.fixtrading.org/standards/fixt/>
>
> Sequence number checking is a vital part of FIX session management. However, a discrepancy in
> the sequence number stream is handled differently for certain classes of FIX messages.
>
> In *ALL* cases except the Sequence Reset - Reset message, the FIX session should be terminated
> if the incoming sequence number is less than expected and the PossDupFlag is not set.
> A Logout message with some descriptive text should be sent to the other side before closing
> the session.
>
>
> Also, it says:
>
> *Sequence number mismatch in case of Logout message:*
> If a message gap was detected, issue a ResendRequest to retrieve all missing messages followed
> by a Logout message which serves as a confirmation of the logout request. DO NOT terminate
> the session. The initiator of the Logout sequence has responsibility to terminate the
> session. This allows the Logout initiator to respond to any ResendRequest message.
> If this side was the initiator of the Logout sequence, then this is a Logout confirmation and
> the session should be immediately terminated upon receipt.
> The only exception to the “do not terminate the session” rule is for an invalid Logon
> attempt. The session acceptor has the right to send a Logout message and terminate the
> session immediately. This minimizes the threat of unauthorized connection attempts.
>
>
> --
> Regards,
>
> Oleg
>
>
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