More on using FreeTDS on a server (was Re: [freetds] Server dumpscore...)

Mike C. mcbp223 at
Thu Apr 22 21:57:37 EDT 2004

> -----Original Message-----
> From: James K. Lowden [mailto:jklowden at]
> Sent: Thursday, April 22, 2004 3:48 PM
> To: mcbp223 at; FreeTDS Development Group
> Subject: Re: More on using FreeTDS on a server (was Re: [freetds] Server
> dumpscore...)

> On Thu, 22 Apr 2004, "Mike C." <mcbp223 at> wrote:
> > it sends TDS_PRELOGIN(0x12), to check if you're talking TDS7+; if you
> > just send done (#253),
> That's a facinating bit of intelligence.  Have you decoded the 0xl2
> packet?
The only attempt to describe the prelogin packet that I could find was an
analysis for a security exploit, do a google for CNETLIBVER. They didn't
analyze however what SQL Server sends back.
I didn't play with it either since I was quite happy to answer either nack
or done, but from what I've seen from the traffic dump, SQL Server 2k sends
back almost the same thing it receives, followed by a done token.

> On my wishlist is to make TDSVER obsolete except for tuning.  Perhaps we
> can start by sending a prelogin packet, fall back to 5.0, then fall back
> to 4.2.  Seems completely doable and worthwhile.
> --jkl
I believe the prelogin dialog is valid only for MS, not for Sybase, so I
don't think you can fall back to 5.0, but to 4.2 sure. Again this is what I
suppose, I don't have access to any Sybase product to check it.


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