pcmu sync.RWMutex
	PacketConn
	done chan bool // signal that indicates server stopped
}

func (ls *localPacketServer) buildup(handler func(*localPacketServer, PacketConn)) error {
	go func() {
		handler(ls, ls.PacketConn)
		close(ls.done)
	}()
	return nil
}

func (ls *localPacketServer) teardown() error {
	ls.pcmu.Lock()
	if ls.PacketConn != nil {

				t.Fatal(err)
			}

			ls := (&packetListener{PacketConn: c1}).newLocalServer()
			defer ls.teardown()
			tpch := make(chan error, 1)
			handler := func(ls *localPacketServer, c PacketConn) { packetTransponder(c, tpch) }
			if err := ls.buildup(handler); err != nil {
				t.Fatal(err)
			}

			trch := make(chan error, 1)
			_, port, err := SplitHostPort(ls.PacketConn.LocalAddr().String())
			if err != nil {

			// suitable address" error on some platforms.
			t.Log(err)
			continue
		}
		ls := (&packetListener{PacketConn: c1}).newLocalServer()
		defer ls.teardown()
		ch := make(chan error, 1)
		handler := func(ls *localPacketServer, c PacketConn) { packetTransponder(c, ch) }
		if err := ls.buildup(handler); err != nil {
			t.Fatal(err)
		}

type addrPortUDPAddr struct {
	netip.AddrPort
}

func (addrPortUDPAddr) Network() string { return "udp" }

// UDPConn is the implementation of the Conn and PacketConn interfaces
// for UDP network connections.
type UDPConn struct {
	conn
}

// SyscallConn returns a raw network connection.
// This implements the syscall.Conn interface.

	}
	n, addr, err := c.readFrom(b)
	if err != nil {
		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return n, addr, err
}

// ReadFrom implements the [PacketConn] ReadFrom method.
func (c *UnixConn) ReadFrom(b []byte) (int, Addr, error) {
	if !c.ok() {
		return 0, nil, syscall.EINVAL
	}
	n, addr, err := c.readFrom(b)
	if err != nil {

	addrs, err := DefaultResolver.resolveAddrList(ctx, "listen", network, address, nil)
	if err != nil {
		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: nil, Err: err}
	}
	sl := &sysListener{
		ListenConfig: *lc,
		network:      network,
		address:      address,
	}
	var c PacketConn
	la := addrs.first(isIPv4)
	switch la := la.(type) {

	defer close(ch)
	handler := func(ls *localPacketServer, c PacketConn) {
		if dst, ok := <-ch; ok {
			c.WriteTo([]byte("READFROM TIMEOUT TEST"), dst)
		}
	}
	ls := newLocalPacketServer(t, "udp")
	defer ls.teardown()
	if err := ls.buildup(handler); err != nil {
		t.Fatal(err)
	}

	host, _, err := SplitHostPort(ls.PacketConn.LocalAddr().String())
	if err != nil {
		t.Fatal(err)
	}

	case <-up:
	}
	t.Cleanup(func() { _ = server.Shutdown() })
	server.Addr = server.PacketConn.LocalAddr().String()

	select {
	case <-time.After(time.Second * 10):
		t.Fatalf("setup timeout")
	case <-up:
	}
	t.Cleanup(func() { _ = tcp.Shutdown() })
	t.Cleanup(func() { _ = server.Shutdown() })
	tcp.Addr = server.PacketConn.LocalAddr().String()
	return server.Addr
}

	if err != nil {
		err = &OpError{Op: "file", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return
}

// PacketConn is a generic packet-oriented network connection.
//
// Multiple goroutines may invoke methods on a PacketConn simultaneously.
type PacketConn interface {
	// ReadFrom reads a packet from the connection,
	// copying the payload into p. It returns the number of

		for i := 0; i < 5; i++ {
			cs, err := newDualStackPacketListener()
			if err != nil {
				t.Fatal(err)
			}
			port := cs[0].port()
			for _, c := range cs {
				c.Close()
			}
			var c1 PacketConn
			c1, firstErr = ListenPacket(tt.network1, JoinHostPort(tt.address1, port))
			if firstErr != nil {
				continue
			}
			if err := checkFirstListener(tt.network1, c1); err != nil {
				c1.Close()