Re: [Boost-users] [asio] using with mdns/dns-sd?

From: William H. Schultz (whschultz_at_[hidden])
Date: 2008-08-04 22:53:59

As the implementer of wxDNSSD (Bonjour for wxWidgets), I can pretty  
easily state that Bonjour doesn't need any access to your actual  
socket at all.  Also, since it uses port 5353, Administrator/root  
access is also not needed.  Because this is wholly independent of your  
actual socket, you can advertise services on any port, whether they  
actually exist or not.

I have learned that iTunes--which does not *require* Bonjour be  
installed--is statically linked to Bonjour.  If Bonjour is installed,  
it uses the installed mDNS responder.  If not, it runs its own.

http://wxcode.sourceforge.net/complist.php?compperpage=1000&viewmode=full&browseby=category&section=networking&page=1
http://trac.wxwidgets.org/ticket/9777

-------------------------------
Hank Schultz
Cedrus Corporation
http://www.cedrus.com/

On Aug 3, 2008, at 11:40 PM, Matt Gruenke wrote:

> I know a bit about mDNS, and I think DNS-SD is just a way to  
> implement service discovery on top of DNS.
>
> The lookup part of mDNS should be implemented at the system level.   
> On a posix system w/ mDNS support, the lookup is normally handled  
> transparently via gethostbyname() and therefore requires no special  
> support from ASIO.  Two ways I've seen this done are via custom  
> support in the C library and via a plug-in (specifically, a shared  
> library that's specified via /etc/nsswitch.conf).  For scalability  
> reasons, it is ideal if the lookup consults a daemon process or  
> service running on the local machine that can both listen for  
> announcements and maintain a cache from which to answer duplicate  
> queries.
>
> I think the Windows install of Bonjour has a way of extending the  
> normal DNS lookup mechanism to support mDNS, as well.  This is  
> necessary for use of mDNS from Windows XP, as it lacks built-in  
> support.  I can't say the same for Windows Vista, however.
>
> I'm not familiar with the other side (i.e. announcements), but I  
> wonder whether typical OS security models permit this to be done at  
> the application level (i.e. if the user is not running as root or  
> local Administrator).  If that's the case, then your app would have  
> to communicate with a service which supports mDNS announcements for  
> that platform - and I'm pretty sure there's no standard way to do  
> that.
>
>
> You might find more interest, on the asio-users mailing list:
>
>   http://sourceforge.net/mail/?group_id=122478
>
>
> Matt
>
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users