[Winpcap-users] trouble about CIFS/SMB protocol

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Hello, my name is wan.

Now,i am developing a packet analysis tool base on winpcap(4.0.1).
My main focus is on protocol CIFS/SMB(Server Message Block).

We use wireshark or ethereal to see the file access packet
from client to operate files on file server.

Sometimes we find AccountName(Account Name), NativeOS(OS of client)
in the SMB_COM_SESSION_SETUP_ANDX command packet(request)
is set to nothing.

I just want to know the reason and timing.Any information is welcome.

Thanks in advance.