Re: [Boost-users] asio tcp::resolver, service resolution

On Thursday, August 25, 2011 11:50 PM, Lloyd wrote:

Top post moved to bottom. Please don't top post.

On Thu, Aug 25, 2011 at 9:22 PM, Andrew Holden wrote:

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On Thursday, August 25, 2011 11:21 AM, Lloyd wrote:

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In documentation I saw that using tcp::resolver::query constructor it is possible to resolve domain.name as well as service name, as shown in the following code fragment.

boost::asio::io_service ios; boost::asio::ip::tcp::resolver resolver(ios); boost::asio::ip::tcp::resolver::query query("mydomain.com","myservice");

Here 'myservice' is not a well known service (port number).

For resolving 'myservice' where should I add the port number? In my domain name server's (BIND) /etc/services file or in my local systems services file?

Or is it 'really' possible to resolve a service name?

The easiest method is to include the service port number as a string. For example, if you're listening on port 12345, your query would be:

boost::asio::ip::tcp::resolver::query query("mydomain.com","12345");

If you hope your program will be widely distributed, then it might to

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worth your while to register your port name with IANA and wait for your and your clients' OS vender to update the "services" file (/etc/services or c:\windows\system32\drivers\etc\sevices).

So the port resolution is not as easy as domain name resolution

Why the DNS protocol can't be extended to resolve services also? So many people must have faced this issue, and why didn't thay think in this way? Is there any technical barrier?

Thanks a lot, Lloyd

I did some searching, and it seems that RFC 2782 defines a "SRV" DNS record for that purpose. I'm not sure how you would access these records in asio, though. Perhaps someone else knows more than I.