split server startup helpers

cmd/server/network.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"net"
+	"net/http"
+	"time"
+)
+
+// getLocalIP returns the first non-loopback IPv4 address of the machine.
+// Falls back to "localhost" if no suitable interface is found.
+func getLocalIP() string {
+	interfaces, err := net.Interfaces()
+	if err != nil {
+		return "localhost"
+	}
+	for _, iface := range interfaces {
+		if iface.Flags&net.FlagUp == 0 || iface.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+		addrs, err := iface.Addrs()
+		if err != nil {
+			continue
+		}
+		for _, addr := range addrs {
+			switch v := addr.(type) {
+			case *net.IPNet:
+				if ip := v.IP.To4(); ip != nil {
+					return ip.String()
+				}
+			}
+		}
+	}
+	return "localhost"
+}
+
+// getPublicIP tries to detect the public-facing IP by querying ipify.org.
+// Returns empty string if detection fails (e.g. no internet, timeout).
+func getPublicIP(timeout time.Duration) string {
+	client := &http.Client{Timeout: timeout}
+	resp, err := client.Get("https://api.ipify.org")
+	if err != nil {
+		return ""
+	}
+	defer resp.Body.Close()
+	buf := make([]byte, 64)
+	n, err := resp.Body.Read(buf)
+	if err != nil || n == 0 || resp.StatusCode != http.StatusOK {
+		return ""
+	}
+	return string(buf[:n])
+}