Pir is a simple library for facilitating in device discovery on a LAN.

go get github.com/jerluc/pir

git clone https://github.com/jerluc/pir.git
cd pir
go install

// Start a healthcheck server
healthcheck := pir.NewHealthCheck()
healthcheck.Start()

// Create a new peer
peer, _ := pir.NewPeer("tcp://10.1.1.1:80", healthcheck.URISpec())

// Join the group on port 9999
group := pir.NewGroup(group, 9999)
peer.Join(group)

group.AddListener(func(event pir.MembershipEvent) bool {
  fmt.Println("Membership change event has occurred:", event)
  return true
})

Presently, this is done using a fairly common discovery protocol:

• New peers join a group by connecting to a multicast UDP broadcast address.
  • Once joined, each peer broadcasts a simple payload consisting of the participating group, peer ID, healthcheck URI, and communications URI: GROUP_NAME|UUID4|proto://x.x.x.x:xxxxx|proto://x.x.x.x:xxxxx
• Each participating peer in the group consumes these broadcasts, creating and updating peer trackers. Trackers are updated by attempting to send and receive data over the healthcheck URI:
  • Each successful send+receive improves tracker health
  • Each failure or timeout degrades tracker health
• When tracker health degrades beyond a certain threshold, the tracker is removed, rendering the tracked peer invisible to the tracker