dss.lnmu.Lock()
	for i := range dss.lns {
		if network == dss.lns[i].network && dss.lns[i].Listener != nil {
			dss.lns[i].Listener.Close()
			<-dss.lns[i].done
			dss.lns[i].Listener = nil
		}
	}
	dss.lnmu.Unlock()
	return nil
}

func (dss *dualStackServer) teardown() error {
	dss.lnmu.Lock()
	for i := range dss.lns {
		if dss.lns[i].Listener != nil {
			dss.lns[i].Listener.Close()

)

// hcode is a huffman code with a bit code and bit length.
type hcode struct {
	code, len uint16
}

type huffmanEncoder struct {
	codes     []hcode
	freqcache []literalNode
	bitCount  [17]int32
	lns       byLiteral // stored to avoid repeated allocation in generate
	lfs       byFreq    // stored to avoid repeated allocation in generate
}

type literalNode struct {
	literal uint16
	freq    int32
}

			tt.xerr = nil
		}
		var firstErr, secondErr error
		for i := 0; i < 5; i++ {
			lns, err := newDualStackListener()
			if err != nil {
				t.Fatal(err)
			}
			port := lns[0].port()
			for _, ln := range lns {
				ln.Close()
			}
			var ln1 Listener
			ln1, firstErr = Listen(tt.network1, JoinHostPort(tt.address1, port))
			if firstErr != nil {

		if err != nil {
			t.Fatal(err)
		}
		defer dss.teardown()
		if err := dss.buildup(handler); err != nil {
			t.Fatal(err)
		}

		d := &Dialer{DualStack: dualstack, Timeout: timeout}
		for range dss.lns {
			c, err := d.Dial("tcp", JoinHostPort("localhost", dss.port))
			if err != nil {
				t.Error(err)
				continue
			}
			switch addr := c.LocalAddr().(*TCPAddr); {
			case addr.IP.To4() != nil: