reorganize; add stopwatch to dlna player for play time tracking

backend/util/util.go

@@ -1,7 +1,9 @@
 package util
 
 import (
+	"fmt"
 	"io"
+	"net"
 	"os"
 )
 
@@ -21,3 +23,30 @@ func CopyFile(srcPath, dstPath string) error {
 	_, err = io.Copy(fout, fin)
 	return err
 }
+
+func GetLocalIP() (string, error) {
+	interfaces, err := net.Interfaces()
+	if err != nil {
+		return "", err
+	}
+
+	for _, iface := range interfaces {
+		if iface.Flags&net.FlagUp == 0 || iface.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+
+		addrs, err := iface.Addrs()
+		if err != nil {
+			return "", err
+		}
+
+		for _, addr := range addrs {
+			ipnet, ok := addr.(*net.IPNet)
+			if ok && !ipnet.IP.IsLoopback() && ipnet.IP.To4() != nil {
+				return ipnet.IP.String(), nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("no suitable interface found")
+}