ln1.Close()
			t.Fatal(err)
		}
		ln2, err := Listen(tt.network, JoinHostPort(tt.address, ln1.(*TCPListener).port()))
		if err == nil {
			ln2.Close()
		}
		if err := checkSecondListener(tt.network, tt.address, err); err != nil {
			ln1.Close()
			t.Fatal(err)
		}
		ln1.Close()
	}
}

var udpListenerTests = []struct {
	network string
	address string
}{
	{"udp", ""},