mox!

mox-/ip.go

@@ -0,0 +1,21 @@
+package mox
+
+import (
+	"net"
+)
+
+// Network returns tcp4 or tcp6, depending on the ip.
+// This network can be passed to Listen instead of "tcp", which may start listening
+// on both ipv4 and ipv6 for addresses 0.0.0.0 and ::, which can lead to errors
+// about the port already being in use.
+// For invalid IPs, "tcp" is returned.
+func Network(ip string) string {
+	v := net.ParseIP(ip)
+	if v == nil {
+		return "tcp"
+	}
+	if v.To4() != nil {
+		return "tcp4"
+	}
+	return "tcp6"
+}