How does an application running on a gateway intially discover the Mesh Local EID of all other devices on a Thread network?
The Thread Protocol does not inherently provide a device/endpoint discovery service. It is possible to use something like multicast ping to solicit responses from all devices in the network, but that is not ideal if you are looking for select endpoints or want additional control over the discovery protocol. As is typical with IP-based protocols, device/endpoint discovery is often provided by a higher-layer service (e.g. DNS, application, etc.).
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For UDP (Multicasts), multiple applications can subscribe to the same port.
If one packet has arrived from client, which application receive it?
Nowadays, mDNS discovery is very popular in LAN D2D use cases. Different applications may bundle different mDNS discovery modules, which leads to the fact that multiple applications listen to the same port. When one packet comes, which application receive it? Or all get notified?
I'm newbie to DDS/Fast-RTPS.
Based on my understanding, the discovery is LAN-based. It failed to discover a node which is not in the same LAN. is it correct?
I'm wondering if we can use fast-rtps to communication across networks?
ps. let's ignore NAT/Firewall issues. Assuming we have a IP/TCP full reachable network environment.
DDS uses Multicast UDP. If your switches and other network infrastructure is set to swallow Multicast packets, or if the TTL is set too low, then the default discovery implementation of DDS will not complete/be seen.
You can up the TTL on your infrastructure, or you can tell the DDS libraries to target specific addresses (see the documentation for your provider's libraries).
http://activemq.apache.org/networks-of-brokers.html
I'm trying activemq network of brokers, following above article.
It works all fine with a fixed list of URIs.
But I have some problem with the multicast discovery. That is, the network bridge between two activemqs on the same machine can be started. But the bridge cannot establish between different machines(I tried telnet, it is ok).
I don't know which part went wrong. So I want to ask that is these two kind of network just difference in configuration?
Telnet is proving that Unicast networking is working, multicast may requires additional configuration in your network.
Are those machines in the same subnet?
Is there a router or Layer 3 switch between them? (it would then requires to be configured if the answer is yes..)
You could use iperf to test the multicast connectivity, you can look at Generating multicast traffic article to know how to do that.
What is the most simple and straightforward approach for serverless P2P UDP chat in Boost Asio? The chat will work across the internet. There are ready UDP examples but they all maintain client-server approach!
I'm assuming that by serverless you mean a P2P network without a central control server.
IMO your question has little to do with boost-asio. asio is a cross-platform network library. You seem to be asking more of a network engineering type question and asio is just one of the tools you can use for implementation.
The examples are client-server in that the example applications possibly fall under the client-server architecture. However the socket code (or asio usage) used to send and receive messages will look the same irrespective of client-server or P2P applications i.e. you send a message to an address and you receive messages on a specified port. The differences will come in at the protocol layer, but this has nothing to do with asio per se.
The following may or may not be of interest to you: there is no simple way IMO: users located behind firewalls and NAT means that you need to use techniques such as STUN, TURN and ICE to resolve addresses or in the worst case relay data. All these designs require a server.
Can anyone tell be where to use the UDP protocol except live streaming of music/video? What are default usecases for UDP?
UDP is also good for broadcast, such as service discovery - finding that newly plugged in printer.
Also of note is that broadcast is anonymous, you don't need to specify target hosts, as such it can form the foundation of a convenient plug-and-play or high-availability network.
UDP is stateless and is good for applications that have large numbers of clients connecting to a server such as time servers or DNS. The fact that no connection has to established and maintained reduces the memory required by the server. There is no handshaking involved and so this reduces the traffic on the network. On the downside, if the information transferred requires multiple packets there is no transmission control to ensure that all packets arrive and in the correct order - but in games packets lost are probably better than late or disordered.
Anything else where you need performance but can survive if a packet gets lost along the way. Multiplayer games come to mind, for example.
A very common use case is DNS, since the overhead of creating a TCP connection would by far outweight the actual payload.
Additional use cases are NTP (network time service) and most video games.
I use UDP to add chat capabilities to our applications. No need to create a server. It is also useful to dispatch events to all users of our applications.