Not responding to "QU" questions

[michaelosthege]

@gaviriar and I discovered a problem with queries. A service was not responding to PTR queries issued by a Java client, while responding to PTR queries originating from a C# client that uses this library.

The corresponding log (awesome logging, by the way!) shows that all queries were received, but a response was only sent for the first:

Upon investgation with Wireshark, I found that the two libraries (this one vs. the Java alternative) issued different PTR queries:

So the Java library issued a QU question, as described in RFC6769 section 5.4:

To avoid large floods of potentially unnecessary responses in these
cases, Multicast DNS defines the top bit in the class field of a DNS
question as the unicast-response bit. When this bit is set in a
question, it indicates that the querier is willing to accept unicast
replies in response to this specific query, as well as the usual
multicast responses. These questions requesting unicast responses
are referred to as "QU" questions, to distinguish them from the more
usual questions requesting multicast responses ("QM" questions). A
Multicast DNS querier sending its initial batch of questions
immediately on wake from sleep or interface activation SHOULD set the
unicast-response bit in those questions.

As far as I can tell this is completely okay behavior by the Java client, but net-mdns should have responded.

Since the logger doesn't show any errors, I assume that the condition in ServiceDiscovery.cs#208 is fulfilled and this is some kind of parsing problem, @richardschneider ?

cheers

[richardschneider]

@michaelosthege could you try the new build and see if #51 solves this issue.

Cheers

[michaelosthege]

@richardschneider yes, I tested it with 0.16.1 from the CI build and it works!
Can you release it on NuGet then?

Thank you for fixing this so fast!