Multiple registrations with same name

[soundprojects]

Hi

When attempting to register the same service twice, the second attempt doesn't seem to register a service at all.

The expected result would be that the name is made unique by adding a number for example MyService (1). Is there a setting to make this happen ?

Thanks!

[quilir]

As far as I see it is not possible without making changes inside the crate.

Mapping name -> id keeps only last registered service for every name:

rust-mdns/src/services.rs

Lines 13 to 21 in 0974ab4

	pub struct ServicesInner {
	hostname: Name<'static>,
	/// main index
	by_id: HashMap<usize, ServiceData>,
	/// maps to id
	by_type: MultiMap<Name<'static>, usize>,
	/// maps to id
	by_name: HashMap<Name<'static>, usize>,
	}

It could be MultiMap instead to allow the responder to quickly find multiple services with the same name.

If you want to rename duplicate service, you can do it in this method:

rust-mdns/src/services.rs

Lines 50 to 61 in 0974ab4

	pub fn register(&mut self, svc: ServiceData) -> usize {
	let mut id = thread_rng().gen::<usize>();
	while self.by_id.contains_key(&id) {
	id = thread_rng().gen::<usize>();
	}
	self.by_type.insert(svc.typ.clone(), id);
	self.by_name.insert(svc.name.clone(), id);
	self.by_id.insert(id, svc);
	id
	}

but I think it is not a good idea to do that. If someone will query for exactly MyService (it is common in mDNS), he won't know that you have some MyService (1) too.

[soundprojects]

Ah right I see. I think many Bonjour libraries do implement this when there is a name conflict as this does make it possible to run multiple local instances with a hardcoded name. What do you think?

[quilir]

You're right that this is recommended way. I've read about it and found this:

https://tools.ietf.org/html/rfc6763#appendix-D

I was focused too much on queries that I make in my project - programmatically discovering all services with some name. Renaming in that way might cause too much trouble to be worth it. I would rather modify this crate to allow multiple services with the same name on one publisher.

But it is probably not the most common case. Results of mDNS queries are often presented on UI and user wants to have clear and distinguishable names.