NyanSD

NyanSD (Nyanko Service Discovery) is a simple yet versatile protocol aimed at providing everything from small network-based applications to entire operating systems with the ability to perform network-based service discovery. While similar to DNS-SD and mDNS, it distinguishes itself by being exceedingly simple to implement.

Both a daemon and client utility are available, as well as a reference client and server implementation.

Quick install

To quickly build and install the NyanSD library, daemon and client utility, on Linux platforms the installation script can be used. After cloning the project to the target system, simply run from the project root:

sudo ./install_nyansd.sh

This will install the libPoco dependency automatically. A current (C++17) GCC/Clang compiler and utilities are expected to be already installed.

Supported platforms: Linux with the apt, pacman or apk package managers. Supported service controllers: systemd & openrc.

Daemon

The NyanSD daemon is found in the daemon/ folder of the project. It can be used on any major platform, including Windows and Linux.

See its documentation for further details on building and running it.

Client

A simple client called nyansd-browse is provided in the browse/ folder of the project. It can be built using the Makefile in that same folder and the resulting binary copied from the browse/bin/ folder.

This client will scan the network for any NyanSD daemons on the default port (11310) and report found services.

Reference implementation

The C++-based reference implementation of the protocol. It requires a C++11 capable compiler and the LibPoco dependency to be installed.

Using the provided Makefile in the root of the project the entire project (library, client and server) can be built by executing:

make

The library (libnyansd.so.1 & libnyansd.a) can be installed using:

sudo make install

At this point the client and server are still rudimentary, but serve to demonstrate the use of the NyanSD reference API. E.g. the client:

int main() {
	std::vector queries;
	std::vector responses;
	
	NYSD_query query;
	query.protocol = NYSD_PROTOCOL_ALL;
	queries.push_back(query);
	
	std::cout << "Sending query..." << std::endl;
	NyanSD::sendQuery(11310, queries, responses);
	
	// Print out responses.
	std::cout << "Received " << responses.size() << " responses." << std::endl;
	for (int i = 0; i < responses.size(); ++i) {
		std::cout << "Got service " << responses[i].service << " on host " << responses[i].hostname
					<< ", IPv4 " << NyanSD::ipv4_uintToString(responses[i].ipv4) 
					<< ", IPv6 " << responses[i].ipv6
					<< ", port " << (uint16_t) responses[i].port << std::endl;
	}
	
	return 0;
}

The above client composes a simple query to get all services available on the network, using port 11310. This means that all NyanSD listening clients on the network ('servers') that are listening on that port will receive the broadcast message.

Note: Since all network interfaces are scanned, if a service is reachable via more than one route, the same service's records will be returned more than once.

The server:

int main() {
	// Add the service records.
	NYSD_service sv;
	sv.port = 11310;
	sv.protocol = NYSD_PROTOCOL_TCP;
	sv.service = "HelloService";
	
	NyanSD::addService(sv);
	
	// Start the server.
	NyanSD::startListener(11310);
	
	// Wait for the server to be terminated here.
	
	// Stop the server.
	NyanSD::stopListener();
	
	return 0;
}

The server can contain a large number of service records, none of which have to be running on that particular host, but can be elsewhere on the network too. See the protocol notes in the next section for further details.

Protocol

The protocol is described in the project's requirements document: NyanSD overview and requirements.

It's a simple binary protocol, little endian (LE)-based. The reference implementation uses UDP broadcast to find services on the network.

Disclaimer

This project is provided with no guarantees as to its functioning or fitness for a particular purpose.