commit 07ddf7e87bf1393c096c23b2c2b363b1c990416e
Author: Jakob Borg <jakob@nym.se>
Date:   Sun Dec 22 21:35:05 2013 -0500

    External discover

diff --git a/cmd/discosrv/main.go b/cmd/discosrv/main.go
new file mode 100644
index 00000000..2941dd9c
--- /dev/null
+++ b/cmd/discosrv/main.go
@@ -0,0 +1,74 @@
+package main
+
+import (
+	"log"
+	"net"
+	"sync"
+
+	"github.com/calmh/syncthing/discover"
+)
+
+type Node struct {
+	IP   []byte
+	Port uint16
+}
+
+var (
+	nodes = make(map[string]Node)
+	lock  sync.Mutex
+)
+
+func main() {
+	addr, _ := net.ResolveUDPAddr("udp", ":22025")
+	conn, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		panic(err)
+	}
+
+	var buf = make([]byte, 1024)
+	for {
+		n, addr, err := conn.ReadFromUDP(buf)
+		if err != nil {
+			panic(err)
+		}
+		pkt, err := discover.DecodePacket(buf[:n])
+		if err != nil {
+			log.Println("Warning:", err)
+			continue
+		}
+
+		switch pkt.Magic {
+		case 0x20121025:
+			// Announcement
+			//lock.Lock()
+			ip := addr.IP.To4()
+			if ip == nil {
+				ip = addr.IP.To16()
+			}
+			node := Node{ip, uint16(pkt.Port)}
+			log.Println("<-", pkt.ID, node)
+			nodes[pkt.ID] = node
+			//lock.Unlock()
+		case 0x19760309:
+			// Query
+			//lock.Lock()
+			node, ok := nodes[pkt.ID]
+			//lock.Unlock()
+			if ok {
+				pkt := discover.Packet{
+					Magic: 0x20121025,
+					ID:    pkt.ID,
+					Port:  node.Port,
+					IP:    node.IP,
+				}
+				_, _, err = conn.WriteMsgUDP(discover.EncodePacket(pkt), nil, addr)
+				if err != nil {
+					log.Println("Warning:", err)
+				} else {
+					log.Println("->", pkt.ID, node)
+				}
+			}
+		}
+
+	}
+}