multicast receive address

[michieldwitte]

When using send_all_coap and using a create_receiver_for receiving all the responses,
we had a requirement to also know where the responses came from.

This fixes that, however I'm not really happy with the exact state of this MR yet.
I'm open for suggestions/improvements to implement!

[Covertness]

My advice is to add a new function rather than change the existed function. Like recv and recv_from in the UdpSocket. Add a new function will make minimal changes.

[michieldwitte]

It all relies on the TransportSynchronizer containing UnboundedSender<IoResult<Packet>> which I need to change to AddressedPacket either way. This forces a lot of changes, I can't find a way around that ...

[Covertness]

Maybe you can extend the defination of the packet. I don't think it's appropriate that do this in the client.

[michieldwitte]

The packet inside coap-lite is the implementation of the RFC message format https://datatracker.ietf.org/doc/html/rfc7252#page-16
Also as far as I can see coap-lite is agnostic of transport, so I don't think it should be done there ...

[Covertness]

The source of a packet is an attribute of packet. The Clang CoAP library implement it by this way: https://github.com/obgm/libcoap/blob/develop/include/coap3/coap_io_internal.h#L224

[michieldwitte]

It's different naming, but boils down to the same thing.
libcoap's coap_packet_t would be AddressedPacket
and payload would be Packet
Maybe coap-lite's "Packet" could better be renamed to "Message".

Maybe we could do this in the client

use coap_lite::Packet as Message

#[derive(Debug, Clone)]
pub struct Packet {
    pub address: SocketAddr,
    pub message: Message,
}

This would probably make the diff smaller, but would eventually be the same thing.

[Covertness]

I think it's better. A terse word reduce the difficulty of code reader.

[michieldwitte]

Should be in a better state now

[Covertness]

https://github.com/Covertness/coap-rs/actions/runs/9604680590/job/26546238545?pr=101 has error. Please check.

[coveralls]

coverage: 82.19% (+0.02%) from 82.169%
when pulling 759258b on michieldwitte:multicast_receive_address
into c120146 on Covertness:master.