Change -port to -listen with flexible address format

Supports host:port, host, or :port for binding to specific
interfaces. Useful for running alongside other ArtNet software.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

artnet/receiver.go

@@ -20,12 +20,7 @@ type Receiver struct {
 }
 
 // NewReceiver creates a new ArtNet receiver
-func NewReceiver(port int, handler PacketHandler) (*Receiver, error) {
-	addr := &net.UDPAddr{
-		Port: port,
-		IP:   net.IPv4zero,
-	}
-
+func NewReceiver(addr *net.UDPAddr, handler PacketHandler) (*Receiver, error) {
 	conn, err := net.ListenUDP("udp4", addr)
 	if err != nil {
 		return nil, err

config.example.toml

@@ -1,5 +1,5 @@
 # artmap configuration
-# Run with: go run . -config config.toml [-port 6454] [-broadcast 2.255.255.255]
+# Run with: go run . -config config.toml [-listen :6454] [-broadcast 2.255.255.255]
 
 # Address format:
 #   from: universe[:channels]  - range specifies which channels to read

main.go

@@ -7,6 +7,8 @@ import (
 	"net"
 	"os"
 	"os/signal"
+	"strconv"
+	"strings"
 	"syscall"
 
 	"github.com/gopatchy/artmap/artnet"
@@ -25,11 +27,17 @@ type App struct {
 
 func main() {
 	configPath := flag.String("config", "config.toml", "path to config file")
-	listenPort := flag.Int("port", artnet.Port, "ArtNet listen port")
+	listenAddr := flag.String("listen", ":6454", "listen address (host:port, host, or :port)")
 	broadcastAddr := flag.String("broadcast", "2.255.255.255", "ArtNet broadcast address")
 	debug := flag.Bool("debug", false, "log ArtNet packets")
 	flag.Parse()
 
+	// Parse listen address
+	addr, err := parseListenAddr(*listenAddr)
+	if err != nil {
+		log.Fatalf("invalid listen address: %v", err)
+	}
+
 	// Load config
 	cfg, err := config.Load(*configPath)
 	if err != nil {
@@ -70,7 +78,7 @@ func main() {
 	}
 
 	// Create receiver
-	receiver, err := artnet.NewReceiver(*listenPort, app)
+	receiver, err := artnet.NewReceiver(addr, app)
 	if err != nil {
 		log.Fatalf("failed to create receiver: %v", err)
 	}
@@ -80,7 +88,7 @@ func main() {
 	receiver.Start()
 	discovery.Start()
 
-	log.Printf("listening on port %d", *listenPort)
+	log.Printf("listening on %s", addr)
 	log.Printf("broadcasting to %s", *broadcastAddr)
 
 	// Wait for interrupt
@@ -155,3 +163,43 @@ func init() {
 	fmt.Println("artmap - ArtNet Remapping Proxy")
 	fmt.Println()
 }
+
+// parseListenAddr parses listen address formats:
+// - "host:port" -> bind to specific host and port
+// - "host" -> bind to specific host, default port
+// - ":port" -> bind to all interfaces, specific port
+func parseListenAddr(s string) (*net.UDPAddr, error) {
+	var host string
+	var port int
+
+	if strings.Contains(s, ":") {
+		h, p, err := net.SplitHostPort(s)
+		if err != nil {
+			return nil, err
+		}
+		host = h
+		if p == "" {
+			port = artnet.Port
+		} else {
+			port, err = strconv.Atoi(p)
+			if err != nil {
+				return nil, err
+			}
+		}
+	} else {
+		host = s
+		port = artnet.Port
+	}
+
+	var ip net.IP
+	if host == "" {
+		ip = net.IPv4zero
+	} else {
+		ip = net.ParseIP(host)
+		if ip == nil {
+			return nil, fmt.Errorf("invalid IP address: %s", host)
+		}
+	}
+
+	return &net.UDPAddr{IP: ip, Port: port}, nil
+}