[freetds] msdblib (Re: Troubles upgrading to freetds-0.82)

James K. Lowden jklowden at freetds.org
Fri Jun 27 14:16:21 EDT 2008


ZIGLIO, Frediano, VF-IT wrote:
> > = Mmmm... yes, try to use version 4.2 to detect protocol 
> > version, however
> > = every time you'll have 2 connections instead of one
> > 
> > Strange -- does not the server identify itself at the initial 
> > "handshake" or 
> > something? Nothing similar to SMTP's "HELO", for example?
> 
> no, initial handshake is quite different for different protocol
> versions...

Cf. http://www.freetds.org/tds.html#login

TDS is an ancient binary protocol; my db-lib manual is copyright January
1988.  Yes, RFC 821 dates from 1982, but Sybase didn't face the
multiple-implementation quandry that Mr. Postel did.  In fact, Microsoft
only recently added a "pre-login" handshake that does approximately that. 
But of course only SQL Server 2008 understands it; it won't help
distinquish a Sybase server from a Microsoft one, or a TDS 7.0 server from
a TDS 8.0 one.  

I did work out a trial-and-error sequence that gets the right protocol
version, but I never finished adding it to the configuration file parser
and to the documentation. It's on my TODO for version 1.0.  

> > And the same application (or a toolkit like Sybtcl) can not 
> > talk to both types 
> > of servers /at once/, unless it is hacked to change a connection's 
> > settings->msdblib itself, which means, it has to be 
> > FreeTDS-aware, rather 
> > than simply use the vendor's API.

Not at all.  Sybase's and Microsoft's implementations of the db-lib API
are *slightly* different.  If you're accustomed to one or the other, you
can specify through --enable-msdblib which one you want.  That option does
*not* affect the kind of server you can connect to.  FreeTDS can connect
to any TDS server, regardless of how compiled.  

HTH.  

--jkl

P.S. Hey, join the list!  I'm a NetBSD guy myself, but I'm more than happy
to help FreeBSD ports to their thing!  




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