Add sACN universe discovery announcements

main.go

@@ -107,13 +107,17 @@ func main() {
 	}
 	defer artSender.Close()
 
-	// Create sACN sender
 	sacnSender, err := sacn.NewSender("artmap", *sacnInterface)
 	if err != nil {
 		log.Fatalf("sacn sender error: %v", err)
 	}
 	defer sacnSender.Close()
 
+	for _, u := range engine.DestSACNUniverses() {
+		sacnSender.RegisterUniverse(u)
+	}
+	sacnSender.StartDiscovery()
+
 	// Create discovery
 	destNums := engine.DestArtNetUniverses()
 	inputUnivs := make([]artnet.Universe, len(destNums))

remap/engine.go

@@ -92,7 +92,6 @@ func (e *Engine) SourceArtNetUniverses() []uint16 {
 	return result
 }
 
-// DestArtNetUniverses returns destination ArtNet universe numbers (for discovery)
 func (e *Engine) DestArtNetUniverses() []uint16 {
 	seen := make(map[uint16]bool)
 	for _, m := range e.mappings {
@@ -106,3 +105,17 @@ func (e *Engine) DestArtNetUniverses() []uint16 {
 	}
 	return result
 }
+
+func (e *Engine) DestSACNUniverses() []uint16 {
+	seen := make(map[uint16]bool)
+	for _, m := range e.mappings {
+		if m.To.Protocol == config.ProtocolSACN {
+			seen[m.To.Number] = true
+		}
+	}
+	result := make([]uint16, 0, len(seen))
+	for u := range seen {
+		result = append(result, u)
+	}
+	return result
+}

sacn/protocol.go

@@ -8,13 +8,14 @@ import (
 const (
 	Port = 5568
 
-	// ACN packet identifiers
-	ACNPacketIdentifier = 0x41534300 // "ASC\0" + more bytes
+	ACNPacketIdentifier = 0x41534300
 
-	// Vector values
 	VectorRootE131Data      = 0x00000004
+	VectorRootE131Extended  = 0x00000008
 	VectorE131DataPacket    = 0x00000002
+	VectorE131Discovery     = 0x00000002
 	VectorDMPSetProperty    = 0x02
+	VectorUniverseDiscovery = 0x00000001
 )
 
 var (
@@ -92,11 +93,49 @@ func BuildDataPacket(universe uint16, sequence uint8, sourceName string, cid [16
 	return buf
 }
 
-// MulticastAddr returns the multicast address for a given universe
 func MulticastAddr(universe uint16) *net.UDPAddr {
-	// 239.255.{universe_high}.{universe_low}
 	return &net.UDPAddr{
 		IP:   net.IPv4(239, 255, byte(universe>>8), byte(universe&0xff)),
 		Port: Port,
 	}
 }
+
+var DiscoveryAddr = &net.UDPAddr{
+	IP:   net.IPv4(239, 255, 250, 214),
+	Port: Port,
+}
+
+func BuildDiscoveryPacket(sourceName string, cid [16]byte, page, lastPage uint8, universes []uint16) []byte {
+	universeCount := len(universes)
+	if universeCount > 512 {
+		universeCount = 512
+	}
+
+	pktLen := 120 + universeCount*2
+	buf := make([]byte, pktLen)
+
+	binary.BigEndian.PutUint16(buf[0:2], 0x0010)
+	binary.BigEndian.PutUint16(buf[2:4], 0x0000)
+	copy(buf[4:16], packetIdentifier[:])
+	rootLen := pktLen - 16
+	binary.BigEndian.PutUint16(buf[16:18], 0x7000|uint16(rootLen))
+	binary.BigEndian.PutUint32(buf[18:22], VectorRootE131Extended)
+	copy(buf[22:38], cid[:])
+
+	framingLen := pktLen - 38
+	binary.BigEndian.PutUint16(buf[38:40], 0x7000|uint16(framingLen))
+	binary.BigEndian.PutUint32(buf[40:44], VectorE131Discovery)
+	copy(buf[44:108], sourceName)
+	binary.BigEndian.PutUint32(buf[108:112], 0)
+
+	discoveryLen := pktLen - 112
+	binary.BigEndian.PutUint16(buf[112:114], 0x7000|uint16(discoveryLen))
+	binary.BigEndian.PutUint32(buf[114:118], VectorUniverseDiscovery)
+	buf[118] = page
+	buf[119] = lastPage
+	for i := 0; i < universeCount; i++ {
+		binary.BigEndian.PutUint16(buf[120+i*2:122+i*2], universes[i])
+	}
+
+	return buf
+}

sacn/sender.go

@@ -3,18 +3,21 @@ package sacn
 import (
 	"crypto/rand"
 	"net"
+	"sort"
 	"sync"
+	"time"
 
 	"golang.org/x/net/ipv4"
 )
 
-// Sender sends sACN (E1.31) packets
 type Sender struct {
 	conn       *net.UDPConn
 	sourceName string
 	cid        [16]byte
 	sequences  map[uint16]uint8
 	seqMu      sync.Mutex
+	universes  map[uint16]bool
+	done       chan struct{}
 }
 
 // NewSender creates a new sACN sender
@@ -45,6 +48,8 @@ func NewSender(sourceName string, ifaceName string) (*Sender, error) {
 		sourceName: sourceName,
 		cid:        cid,
 		sequences:  make(map[uint16]uint8),
+		universes:  make(map[uint16]bool),
+		done:       make(chan struct{}),
 	}, nil
 }
 
@@ -75,7 +80,65 @@ func (s *Sender) SendDMXUnicast(addr *net.UDPAddr, universe uint16, data []byte)
 	return err
 }
 
-// Close closes the sender
 func (s *Sender) Close() error {
+	select {
+	case <-s.done:
+	default:
+		close(s.done)
+	}
 	return s.conn.Close()
 }
+
+func (s *Sender) RegisterUniverse(universe uint16) {
+	s.seqMu.Lock()
+	s.universes[universe] = true
+	s.seqMu.Unlock()
+}
+
+func (s *Sender) StartDiscovery() {
+	go s.discoveryLoop()
+}
+
+func (s *Sender) discoveryLoop() {
+	ticker := time.NewTicker(10 * time.Second)
+	defer ticker.Stop()
+
+	s.sendDiscovery()
+
+	for {
+		select {
+		case <-s.done:
+			return
+		case <-ticker.C:
+			s.sendDiscovery()
+		}
+	}
+}
+
+func (s *Sender) sendDiscovery() {
+	s.seqMu.Lock()
+	universes := make([]uint16, 0, len(s.universes))
+	for u := range s.universes {
+		universes = append(universes, u)
+	}
+	s.seqMu.Unlock()
+
+	if len(universes) == 0 {
+		return
+	}
+
+	sort.Slice(universes, func(i, j int) bool { return universes[i] < universes[j] })
+
+	const maxPerPage = 512
+	totalPages := (len(universes) + maxPerPage - 1) / maxPerPage
+
+	for page := 0; page < totalPages; page++ {
+		start := page * maxPerPage
+		end := start + maxPerPage
+		if end > len(universes) {
+			end = len(universes)
+		}
+		pkt := BuildDiscoveryPacket(s.sourceName, s.cid, uint8(page), uint8(totalPages-1), universes[start:end])
+		s.conn.WriteToUDP(pkt, DiscoveryAddr)
+	}
+}