_, port, err := SplitHostPort(ln.Addr().String())
	if err != nil {
		t.Fatal(err)
	}
	c, err := Dial("tcp", JoinHostPort("", port))
	if err != nil {
		t.Fatal(err)
	}
	c.Close()
}

func TestDialerDualStackFDLeak(t *testing.T) {
	switch runtime.GOOS {
	case "plan9":
		t.Skipf("%s does not have full support of socktest", runtime.GOOS)
	case "windows":