diff --git a/arp/handler.go b/arp/handler.go
index 076a335..46753e0 100644
--- a/arp/handler.go
+++ b/arp/handler.go
@@ -150,7 +150,7 @@ func (c *Handler) Recv(b []byte) error {
 	var vld lneto.Validator
 	afrm.ValidateSize(&vld)
 	if vld.HasError() {
-		return vld.Err()
+		return vld.ErrPop()
 	}
 	htype, hlen := afrm.Hardware()
 	if htype != c.htype || int(hlen) != len(c.ourHWAddr) {
diff --git a/arp/handler_test.go b/arp/handler_test.go
index 009e293..d97ef6c 100644
--- a/arp/handler_test.go
+++ b/arp/handler_test.go
@@ -114,8 +114,8 @@ func validateARP(t *testing.T, buf []byte) {
 	var vld lneto.Validator
 	afrm.ValidateSize(&vld)
 	if vld.HasError() {
-		t.Errorf("invalid arp: %s", vld.Err())
-	} else if err := vld.Err(); err != nil {
+		t.Errorf("invalid arp: %s", vld.ErrPop())
+	} else if err := vld.ErrPop(); err != nil {
 		panic("unreachable: " + err.Error())
 	}
 }
diff --git a/examples/stack/main.go b/examples/stack/main.go
index 44dfd1b..547f7ac 100644
--- a/examples/stack/main.go
+++ b/examples/stack/main.go
@@ -1,6 +1,8 @@
 package main
 
 import (
+	"crypto/rand"
+	"encoding/binary"
 	"fmt"
 	"log"
 	"log/slog"
@@ -49,7 +51,7 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	handler, err := stack.OpenPassiveTCP(addrPort.Port(), iss)
+	listener, err := stack.OpenTCPListener(addrPort.Port())
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -62,6 +64,7 @@ func main() {
 	const standbyDuration = 5 * time.Second
 	lastHit := time.Now().Add(-standbyDuration)
 	var cap pcap.PacketBreakdown
+	var conn *tcp.Conn
 	for {
 		nread, err := tap.Read(buf[:])
 		if err != nil {
@@ -82,7 +85,25 @@ func main() {
 				lg.Error("recv", slog.String("err", err.Error()), slog.Int("plen", nread))
 			}
 		}
-		doHTTP(handler, &hdr)
+		if conn == nil && listener.NumberOfReadyToAccept() > 0 {
+			conn, err = listener.TryAccept()
+			if err != nil {
+				lg.Error("tryaccept", slog.String("err", err.Error()))
+			}
+			lg.Info("ACCEPT!")
+		}
+		if conn != nil {
+			done, err := doHTTP(conn, &hdr)
+			if done {
+				lg.Info("close forever")
+				conn.Close()
+				conn = nil
+			}
+			if err != nil {
+				lg.Error("doHTTP", slog.String("err", err.Error()))
+			}
+		}
+
 		nw, err := stack.ethernet.Encapsulate(buf[:], 0)
 		if err != nil {
 			lg.Error("handle", slog.String("err", err.Error()))
@@ -115,23 +136,21 @@ func main() {
 	}
 }
 
-func doHTTP(conn *tcp.Conn, hdr *httpraw.Header) error {
+func doHTTP(conn *tcp.Conn, hdr *httpraw.Header) (done bool, err error) {
 	const asRequest = false
 	if conn.State() != tcp.StateEstablished || conn.BufferedInput() == 0 {
-		return nil // No data yet.
+		return false, nil // No data yet.
 	}
 	fmt.Println("state is established; check request and send response")
-	_, err := hdr.ReadFromLimited(conn, hdr.BufferFree())
+	_, err = hdr.ReadFromLimited(conn, hdr.BufferFree())
 	if err != nil {
-		return err
+		return false, err
 	}
 	needMore, err := hdr.TryParse(asRequest)
-	if err != nil {
-		if !needMore {
-			fmt.Println("IT's SO GOVER")
-			conn.Close()
-		}
-		return err
+	if needMore {
+		return false, nil
+	} else if err != nil {
+		return true, err
 	}
 	// HTTP parsed succesfully!
 	fmt.Println("GOT HTTP:\n", hdr.String())
@@ -141,18 +160,18 @@ func doHTTP(conn *tcp.Conn, hdr *httpraw.Header) error {
 	data := `{"ok":true}`
 	response, err := hdr.AppendResponse(nil)
 	if err != nil {
-		return err
+		return true, err
 	}
 	response = append(response, data...)
 	_, err = conn.Write(response)
 	if err != nil {
-		return err
+		return true, err
 	}
 	err = conn.Close()
 	if err != nil {
-		return err
+		return true, err
 	}
-	return nil
+	return true, nil
 }
 
 type Stack struct {
@@ -198,6 +217,7 @@ func (stack *Stack) Reset(ourMAC, gwMAC [6]byte, ip netip.Addr, mtu int) (err er
 	if err != nil {
 		return err
 	}
+
 	return nil
 }
 
@@ -209,6 +229,19 @@ func (stack *Stack) Send(b []byte) (int, error) {
 	return stack.ethernet.Encapsulate(b, 0)
 }
 
+func (stack *Stack) OpenTCPListener(port uint16) (*internet.NodeTCPListener, error) {
+	var listener internet.NodeTCPListener
+	err := listener.Reset(port, naiveTCPPool{})
+	if err != nil {
+		return nil, err
+	}
+	err = stack.tcpports.Register(&listener)
+	if err != nil {
+		return nil, err
+	}
+	return &listener, nil
+}
+
 func (stack *Stack) OpenPassiveTCP(port uint16, iss tcp.Value) (*tcp.Conn, error) {
 	mtu := stack.ethernet.MTU()
 	conn := new(tcp.Conn)
@@ -250,3 +283,25 @@ func getTCPFlags(frames []pcap.Frame, pkt []byte) (flags tcp.Flags) {
 	}
 	return 0
 }
+
+type naiveTCPPool struct {
+}
+
+func (naiveTCPPool) GetTCP() (*tcp.Conn, tcp.Value) {
+	var buf [4]byte
+	rand.Read(buf[:])
+	randVal := binary.LittleEndian.Uint32(buf[:])
+	var conn tcp.Conn
+	err := conn.Configure(&tcp.ConnConfig{
+		RxBuf:             make([]byte, 1024),
+		TxBuf:             make([]byte, 1024),
+		TxPacketQueueSize: 3,
+		Logger:            slog.Default(),
+	})
+	if err != nil {
+		panic(err)
+	}
+	return &conn, tcp.Value(randVal)
+}
+
+func (naiveTCPPool) PutTCP(*tcp.Conn) {}
diff --git a/examples/stackbasic/main.go b/examples/stackbasic/main.go
index 7b9380a..bd3eed9 100644
--- a/examples/stackbasic/main.go
+++ b/examples/stackbasic/main.go
@@ -268,7 +268,7 @@ func (ls *LinkStack) RecvEth(ethFrame []byte) (err error) {
 		goto DROP
 	}
 	efrm.ValidateSize(&vld)
-	if err := vld.Err(); err != nil {
+	if err := vld.ErrPop(); err != nil {
 		return err
 	}
 
diff --git a/internal/ltesto/ltesto.go b/internal/ltesto/ltesto.go
index 2facfef..1e2ce1d 100644
--- a/internal/ltesto/ltesto.go
+++ b/internal/ltesto/ltesto.go
@@ -143,15 +143,15 @@ func (gen *PacketGen) AppendRandomIPv4TCPPacket(dst []byte, rng *rand.Rand, seg
 	}
 	var vld lneto.Validator
 	efrm.ValidateSize(&vld)
-	if err = vld.Err(); err != nil {
+	if err = vld.ErrPop(); err != nil {
 		panic(err)
 	}
 	ifrm.ValidateExceptCRC(&vld)
-	if err = vld.Err(); err != nil {
+	if err = vld.ErrPop(); err != nil {
 		panic(err)
 	}
 	tfrm.ValidateSize(&vld)
-	if err = vld.Err(); err != nil {
+	if err = vld.ErrPop(); err != nil {
 		panic(err)
 	}
 	return dst
diff --git a/internet/node-arp.go b/internet/node-arp.go
index 1a3a184..6efd061 100644
--- a/internet/node-arp.go
+++ b/internet/node-arp.go
@@ -31,7 +31,7 @@ func (narp *NodeARP) Demux(EtherFrame []byte, arpOff int) error {
 	}
 	afrm.ValidateSize(&narp.vld)
 	if narp.vld.HasError() {
-		slog.Error("invalid-ARP", slog.String("err", narp.vld.Err().Error()))
+		slog.Error("invalid-ARP", slog.String("err", narp.vld.ErrPop().Error()))
 		return nil
 	}
 	return narp.handler.Recv(EtherFrame[arpOff:])
diff --git a/internet/node-tcplistener.go b/internet/node-tcplistener.go
index 58e85f9..b8608f1 100644
--- a/internet/node-tcplistener.go
+++ b/internet/node-tcplistener.go
@@ -65,9 +65,36 @@ func (listener *NodeTCPListener) Reset(port uint16, pool tcpPool) error {
 	return nil
 }
 
+func (listener *NodeTCPListener) NumberOfReadyToAccept() (nready int) {
+	if listener.isClosed() {
+		return 0
+	}
+	for _, conn := range listener.ready {
+		if conn == nil {
+			continue
+		}
+		nready++
+	}
+	return nready
+}
+
+func (listener *NodeTCPListener) TryAccept() (*tcp.Conn, error) {
+	if listener.isClosed() {
+		return nil, net.ErrClosed
+	}
+	for i, conn := range listener.ready {
+		if conn == nil {
+			continue
+		}
+		listener.accepted = append(listener.accepted, conn)
+		listener.ready[i] = nil // discard from ready.
+		return conn, nil
+	}
+	return nil, errors.New("no conns available")
+}
+
 func (listener *NodeTCPListener) AcceptRaw() (*tcp.Conn, error) {
 	connid := listener.connID
-
 	for {
 		if listener.isClosed() || connid != listener.connID {
 			return nil, net.ErrClosed
diff --git a/internet/pcap/capture.go b/internet/pcap/capture.go
index 8eab9be..df179a3 100644
--- a/internet/pcap/capture.go
+++ b/internet/pcap/capture.go
@@ -34,7 +34,7 @@ func (pc *PacketBreakdown) CaptureEthernet(dst []Frame, pkt []byte, bitOffset in
 	}
 	efrm.ValidateSize(pc.validator())
 	if pc.validator().HasError() {
-		return dst, pc.validator().Err()
+		return dst, pc.validator().ErrPop()
 	}
 
 	finfo := Frame{
@@ -61,6 +61,8 @@ func (pc *PacketBreakdown) CaptureEthernet(dst []Frame, pkt []byte, bitOffset in
 		dst, err = pc.CaptureARP(dst, pkt, end)
 	case ethernet.TypeIPv4:
 		dst, err = pc.CaptureIPv4(dst, pkt, end)
+	case ethernet.TypeIPv6:
+		dst, err = pc.CaptureIPv6(dst, pkt, end)
 	default:
 		dst = append(dst, remainingFrameInfo(etype, FieldClassPayload, end, octet*len(pkt)))
 	}
@@ -77,7 +79,7 @@ func (pc *PacketBreakdown) CaptureARP(dst []Frame, pkt []byte, bitOffset int) ([
 	}
 	afrm.ValidateSize(pc.validator())
 	if pc.validator().HasError() {
-		return dst, pc.validator().Err()
+		return dst, pc.validator().ErrPop()
 	}
 
 	finfo := Frame{
@@ -129,7 +131,7 @@ func (pc *PacketBreakdown) CaptureIPv6(dst []Frame, pkt []byte, bitOffset int) (
 	}
 	ifrm6.ValidateSize(pc.validator())
 	if pc.validator().HasError() {
-		return dst, pc.validator().Err()
+		return dst, pc.validator().ErrPop()
 	}
 	finfo := Frame{
 		Protocol:        ethernet.TypeIPv6,
@@ -138,7 +140,7 @@ func (pc *PacketBreakdown) CaptureIPv6(dst []Frame, pkt []byte, bitOffset int) (
 	finfo.Fields = append(finfo.Fields, baseIPv6Fields[:]...)
 	dst = append(dst, finfo)
 	proto := ifrm6.NextHeader()
-	end := 40 * octet
+	end := bitOffset + 40*octet
 	return pc.captureIPProto(proto, dst, pkt, end)
 }
 
@@ -152,7 +154,7 @@ func (pc *PacketBreakdown) CaptureIPv4(dst []Frame, pkt []byte, bitOffset int) (
 	}
 	ifrm4.ValidateSize(pc.validator())
 	if pc.validator().HasError() {
-		return dst, pc.validator().Err()
+		return dst, pc.validator().ErrPop()
 	}
 	finfo := Frame{
 		Protocol:        ethernet.TypeIPv4,
@@ -195,7 +197,7 @@ func (pc *PacketBreakdown) CaptureTCP(dst []Frame, pkt []byte, bitOffset int) ([
 	}
 	tfrm.ValidateSize(pc.validator())
 	if pc.validator().HasError() {
-		return dst, pc.validator().Err()
+		return dst, pc.validator().ErrPop()
 	}
 	end := bitOffset + octet*tfrm.HeaderLength()
 	finfo := Frame{
@@ -232,7 +234,7 @@ func (pc *PacketBreakdown) CaptureUDP(dst []Frame, pkt []byte, bitOffset int) ([
 	}
 	ufrm.ValidateSize(pc.validator())
 	if pc.validator().HasError() {
-		return dst, pc.validator().Err()
+		return dst, pc.validator().ErrPop()
 	}
 	finfo := Frame{
 		Protocol:        lneto.IPProtoUDP,
diff --git a/internet/stack-ethernet.go b/internet/stack-ethernet.go
index 8e42205..51802e3 100644
--- a/internet/stack-ethernet.go
+++ b/internet/stack-ethernet.go
@@ -77,7 +77,7 @@ func (ls *StackEthernet) Demux(carrierData []byte, frameOffset int) (err error)
 	}
 	efrm.ValidateSize(&vld)
 	if vld.HasError() {
-		return vld.Err()
+		return vld.ErrPop()
 	}
 
 	for i := range ls.handlers {
diff --git a/internet/stack-ip.go b/internet/stack-ip.go
index 46e16c0..4d5d420 100644
--- a/internet/stack-ip.go
+++ b/internet/stack-ip.go
@@ -78,7 +78,7 @@ func (sb *StackIP) Demux(carrierData []byte, offset int) error {
 	{
 		sb.validator.ResetErr()
 		ifrm.ValidateExceptCRC(&sb.validator)
-		if err = sb.validator.Err(); err != nil {
+		if err = sb.validator.ErrPop(); err != nil {
 			return err
 		}
 		gotCRC := ifrm.CRC()
diff --git a/ipv4/frame_test.go b/ipv4/frame_test.go
index 88f1d25..d13503a 100644
--- a/ipv4/frame_test.go
+++ b/ipv4/frame_test.go
@@ -45,8 +45,8 @@ func TestFrame(t *testing.T) {
 		wantDst := *dst
 		ifrm.ValidateExceptCRC(v)
 		ifrm.ValidateSize(v)
-		if v.Err() != nil {
-			t.Error(v.Err())
+		if v.ErrPop() != nil {
+			t.Error(v.ErrPop())
 		}
 
 		// OPTION+PAYLOAD VALIDATION:
diff --git a/lneto_test.go b/lneto_test.go
index a25a0ae..c0a9e8f 100644
--- a/lneto_test.go
+++ b/lneto_test.go
@@ -137,7 +137,7 @@ func TestIPv4TCPChecksum(t *testing.T) {
 		ifrm.ValidateSize(&vld)
 		tfrm, _ := tcp.NewFrame(ifrm.Payload())
 		tfrm.ValidateExceptCRC(&vld)
-		if err := vld.Err(); err != nil {
+		if err := vld.ErrPop(); err != nil {
 			t.Fatal(err)
 		}
 		wantCRC := ifrm.CRC()
diff --git a/tcp/handler.go b/tcp/handler.go
index 806bf7b..01bcb5e 100644
--- a/tcp/handler.go
+++ b/tcp/handler.go
@@ -144,7 +144,7 @@ func (h *Handler) Recv(incomingPacket []byte) error {
 		return err
 	}
 	tfrm.ValidateExceptCRC(&h.validator)
-	err = h.validator.Err()
+	err = h.validator.ErrPop()
 	if err != nil {
 		return err
 	}
diff --git a/tcp/tcp_test.go b/tcp/tcp_test.go
index 9c59d91..c0937c3 100644
--- a/tcp/tcp_test.go
+++ b/tcp/tcp_test.go
@@ -596,8 +596,8 @@ func parseSegment(t *testing.T, b []byte) (tcp.Segment, []byte) {
 		t.Fatalf("not IPv4")
 	}
 	efrm.ValidateSize(&vld)
-	if err := vld.Err(); err != nil {
-		t.Fatal(vld.Err())
+	if err := vld.ErrPop(); err != nil {
+		t.Fatal(vld.ErrPop())
 	}
 	ifrm, err := ipv4.NewFrame(efrm.Payload())
 	if err != nil {
@@ -611,8 +611,8 @@ func parseSegment(t *testing.T, b []byte) (tcp.Segment, []byte) {
 		t.Fatal("invalid IP version", v)
 	}
 	ifrm.ValidateSize(&vld)
-	if err := vld.Err(); err != nil {
-		t.Fatal(vld.Err())
+	if err := vld.ErrPop(); err != nil {
+		t.Fatal(vld.ErrPop())
 	}
 
 	ipl := ifrm.Payload()
@@ -621,7 +621,7 @@ func parseSegment(t *testing.T, b []byte) (tcp.Segment, []byte) {
 		t.Fatal(err)
 	}
 	tfrm.ValidateSize(&vld)
-	if err := vld.Err(); err != nil {
+	if err := vld.ErrPop(); err != nil {
 		t.Fatal(err)
 	}
 	_ = tfrm.String()
diff --git a/tcp/txqueue.go b/tcp/txqueue.go
index 1bfe450..9463773 100644
--- a/tcp/txqueue.go
+++ b/tcp/txqueue.go
@@ -50,6 +50,7 @@ type ringidx struct {
 // Reset resets the RingTx's internal state to use buf as the main ring buffer and creates or reuses
 // the packet ring buffer.
 func (rtx *ringTx) Reset(buf []byte, maxqueuedPackets int, seq Value) error {
+	buf = buf[:len(buf):len(buf)] // safely omit capacity section.
 	if maxqueuedPackets <= 0 {
 		return errors.New("queued packets <=0")
 	} else if len(buf) < minBufferSize || len(buf) < maxqueuedPackets {
diff --git a/validation.go b/validation.go
index 5b5412d..11fca69 100644
--- a/validation.go
+++ b/validation.go
@@ -39,13 +39,16 @@ func (v *Validator) HasError() bool {
 	return len(v.accum) != 0
 }
 
-func (v *Validator) Err() error {
+// ErrPop returns the error(s) accumulated in the validator and clears them.
+func (v *Validator) ErrPop() (err error) {
 	if len(v.accum) == 1 {
-		return v.accum[0]
-	} else if len(v.accum) == 0 {
-		return nil
+		err = v.accum[0]
+		v.ResetErr()
+	} else if len(v.accum) > 0 {
+		err = errors.Join(v.accum...)
+		v.ResetErr()
 	}
-	return errors.Join(v.accum...)
+	return err
 }
 
 func (v *Validator) gotErr(err error) {