1 files changed, 74 insertions, 0 deletions
diff --git a/m4p/discover.go b/m4p/discover.go
new file mode 100644
index 0000000..a63dde2
--- /dev/null
+++ b/m4p/discover.go
@@ -0,0 +1,74 @@
+package m4p
+
+import (
+	"log"
+	"net"
+)
+
+// Discoverer magic4pc servers.
+type Discoverer struct {
+	ln     *net.UDPConn
+	device chan DeviceInfo
+}
+
+// NewDiscover returns a new Discoverer that listens on the broadcast port.
+func NewDiscoverer(broadcastPort int) (*Discoverer, error) {
+	addr := net.UDPAddr{
+		Port: broadcastPort,
+		IP:   net.ParseIP("0.0.0.0"),
+	}
+
+	ln, err := net.ListenUDP("udp", &addr)
+	if err != nil {
+		panic(err)
+	}
+
+	d := &Discoverer{
+		ln:     ln,
+		device: make(chan DeviceInfo), // Unbuffered, discard when nobody is listening.
+	}
+	go d.discover()
+
+	return d, nil
+}
+
+func (d *Discoverer) discover() {
+	var buf [1024]byte
+	for {
+		n, addr, err := d.ln.ReadFromUDP(buf[:])
+		if err != nil {
+			log.Printf("m4p: Discoverer: discover: read udp packet failed: %v", err)
+			continue
+		}
+
+		m, err := decode(buf[:n])
+		if err != nil {
+			log.Printf("m4p: Discoverer: discover: decode failed: %v", err)
+		}
+
+		switch m.Type {
+		case Magic4PCAdMessage:
+			dev := m.DeviceInfo
+			dev.IPAddr = addr.IP.String()
+			log.Printf("m4p: Discoverer: discover: found device: %#v", dev)
+
+			select {
+			case d.device <- *dev:
+			default:
+			}
+
+		default:
+			log.Printf("m4p: Discoverer: discover: unknown message: %s", m.Type)
+		}
+	}
+}
+
+// NextDevice returns a newly discovered magic4pc server.
+func (d *Discoverer) NextDevice() <-chan DeviceInfo {
+	return d.device
+}
+
+// Close the Discoverer and stop listening for broadcasts.
+func (d *Discoverer) Close() error {
+	return d.ln.Close()
+}