DCT_WIFI/DCT_test/Verify-Transport.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;

namespace DCT_test
{
    public static class TransportRegression
    {
        private static bool fragmentRequests;
        private static void Check(bool value, string message) { if (!value) throw new Exception(message); }
        private static DctPacket Receive(NetworkStream stream)
        {
            var frame = new List<byte>();
            while (true)
            {
                int value = stream.ReadByte();
                if (value < 0) throw new EndOfStreamException();
                frame.Add((byte)value);
                var parsed = DctPacket.ParseStream(frame);
                if (parsed.Count > 0) return parsed[0];
            }
        }
        private static DctPacket Request(NetworkStream stream, byte command, params byte[] payload)
        {
            byte[] bytes = DctPacket.Create(command, payload).Encode();
            WriteFrame(stream, bytes);
            return Receive(stream);
        }

        // Replay the current Android client's transactions over the real TCP listener.
        // No Wi-Fi adapter, firewall, equipment or Android application state is changed.
        public static void RunCurrentAppCompatibility()
        {
            RunCurrentAppCompatibility(null, false);
        }

        public static void RunCurrentAppCompatibility(Func<IPEndPoint, TcpClient> connect, bool fragmented)
        {
            fragmentRequests = fragmented;
            var server = new DctTcpServer();
            int playbackStops = 0;
            server.OnStopPlaybackRequested += () => Interlocked.Increment(ref playbackStops);
            var start = typeof(DctTcpServer).GetMethod("Start", BindingFlags.Instance | BindingFlags.NonPublic,
                null, new[] { typeof(int), typeof(IPAddress), typeof(bool) }, null);
            Check((bool)start.Invoke(server, new object[] { 0, IPAddress.Loopback, false }), "App compatibility listener");
            try
            {
                var listener = (TcpListener)typeof(DctTcpServer).GetField("_listener", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(server);
                using (var client = ConnectClient((IPEndPoint)listener.LocalEndpoint, connect))
                {
                    var stream = client.GetStream();
                    stream.ReadTimeout = 1500;
                    Check(SpinWait.SpinUntil(() => server.ActiveClients.Count == 1, 1000), "TCP attach");
                    ClientSession session = null;
                    foreach (var active in server.ActiveClients) session = active;
                    Check(!session.Streaming && !session.ReadyToMeasure && !stream.DataAvailable,
                        "Wi-Fi/TCP attach must not enable protocol or playback");
                    Check(Request(stream, 0x05).CommandId == 0x85, "Idle connection probe 05 -> 85");
                    Check(!session.Streaming && session.HandshakeMask == 0, "Probe must not connect/start");

                    ConfigureCurrentApp(stream, 0);
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "Current MDB START");
                    Check(SpinWait.SpinUntil(() => session.Streaming, 1000), "MDB stream active after A0");
                    int generation = session.TelemetryGeneration;
                    Check(Request(stream, 0x05).CommandId == 0x85 && session.Streaming &&
                        generation == session.TelemetryGeneration, "Probe must not reset playback or ACK generation");
                    var mdbFrame = DctPacket.Create(0xA3, new byte[] { 1, 0xA0, 7 });
                    server.BroadcastLogPacketAsync(mdbFrame, 0, CancellationToken.None).GetAwaiter().GetResult();
                    CheckFrame(Receive(stream), mdbFrame, "MDB log frame after probe");
                    Write(stream, 0x23, 1);
                    var smFrame = DctPacket.Create(0xA4, new byte[] { 1, 0, 8, 0, 0xFF, 0x7E, 0xA1, 3 });
                    server.BroadcastLogPacketAsync(smFrame, 3, CancellationToken.None).GetAwaiter().GetResult();
                    CheckFrame(Receive(stream), smFrame, "Sensor log frame");
                    Write(stream, 0x24, 1);
                    Check(Request(stream, 0x21).CommandId == 0xA1 && !session.Streaming && session.ReadyToMeasure,
                        "STOP keeps protocol configured on same TCP");
                    Check(Request(stream, 0x05).CommandId == 0x85, "Probe after STOP");
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "Restart after STOP");
                    Check(SpinWait.SpinUntil(() => session.Streaming, 1000), "Restart active");

                    // Current Android stream watchdog replays handshake/configuration on
                    // the existing TCP. ENABLE must retire the previous measurement run.
                    Check(Request(stream, 0x00).CommandId == 0x80, "Recovery ENABLE");
                    Check(!session.Streaming && !session.ReadyToMeasure && session.HandshakeMask == 1 &&
                        session.ConfigurationMask == 0 && session.XcpUseMode == 0, "ENABLE clears old session readiness");
                    Check(Request(stream, 0x20, 1).Payload[0] != 1, "Old settings cannot authorize START");
                    ConfigureCurrentApp(stream, 0);
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "Recovery START after full setup");
                    Check(SpinWait.SpinUntil(() => session.Streaming, 1000), "Recovery stream active");

                    Write(stream, 0x0F);
                    // DISABLE has no 8F response in the PC/current Android protocol.
                    Check(Request(stream, 0x05).CommandId == 0x85, "DISABLE must not leave a fictional 8F response");
                    Check(!session.Streaming && !session.ReadyToMeasure && session.HandshakeMask == 0,
                        "DISABLE ends protocol without closing TCP");
                    Check(Request(stream, 0x20, 1).Payload[0] != 1, "START after DISABLE needs fresh Connect/setup");

                    ConfigureCurrentApp(stream, 1);
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "Current A2L START without MDB commands");
                    Check(SpinWait.SpinUntil(() => session.Streaming, 1000), "XCP stream active");
                    var xcpFrame = DctPacket.Create(0xD0, new byte[] { 0, 1, 2, 0x34, 0x12 });
                    server.BroadcastLogPacketAsync(xcpFrame, 1, CancellationToken.None).GetAwaiter().GetResult();
                    CheckFrame(Receive(stream), xcpFrame, "XCP log frame");
                    Write(stream, 0x50, 1);
                    Check(Request(stream, 0x05).CommandId == 0x85, "Probe after XCP ACK");
                    Check(server.TotalCanAcks == 1 && server.TotalSmAcks == 1 && server.TotalXcpAcks == 1, "Current host ACKs consumed");
                    Check(Request(stream, 0x21).CommandId == 0xA1, "XCP STOP");

                    ConfigureCurrentApp(stream, 2);
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "CAN-only START without MDB/XCP lists");
                    Check(SpinWait.SpinUntil(() => session.Streaming, 1000), "CAN-only stream active");
                    var canFrame = DctPacket.Create(0xA3, new byte[] { 2, 1, 1, 1, 0x24, 2, 1, 7 });
                    server.BroadcastLogPacketAsync(canFrame, 2, CancellationToken.None).GetAwaiter().GetResult();
                    CheckFrame(Receive(stream), canFrame, "CAN-DBC log frame");
                    Write(stream, 0x23, 1);
                    Check(Request(stream, 0x05).CommandId == 0x85 && server.TotalCanAcks == 2, "CAN-only ACK/probe");
                    int stopsBeforeOtherClient = Volatile.Read(ref playbackStops);
                    using (var other = ConnectClient((IPEndPoint)listener.LocalEndpoint, connect))
                    {
                        other.GetStream().ReadTimeout = 1500;
                        Check(Request(other.GetStream(), 0x00).CommandId == 0x80, "Second client Connect");
                        Write(other.GetStream(), 0x0F);
                        Check(Request(other.GetStream(), 0x05).CommandId == 0x85 && session.Streaming &&
                            Volatile.Read(ref playbackStops) == stopsBeforeOtherClient,
                            "Other client's Connect/DISABLE must not stop an active client");
                    }
                    Request(stream, 0x21);
                }
            }
            finally { server.Stop(); fragmentRequests = false; }
            Console.WriteLine("PASS: current Android TCP attach/05/Connect/MDB/STOP/restart/recovery/DISABLE/A2L/CAN-only/ACK parity");
        }

        private static void Write(NetworkStream stream, byte command, params byte[] payload)
        {
            byte[] bytes = DctPacket.Create(command, payload).Encode();
            WriteFrame(stream, bytes);
        }

        private static TcpClient ConnectClient(IPEndPoint endpoint, Func<IPEndPoint, TcpClient> connect)
        {
            if (connect != null) return connect(endpoint);
            var client = new TcpClient();
            try { client.Connect(endpoint); return client; }
            catch { client.Dispose(); throw; }
        }

        private static void WriteFrame(NetworkStream stream, byte[] bytes)
        {
            if (!fragmentRequests) { stream.Write(bytes, 0, bytes.Length); return; }
            for (int i = 0; i < bytes.Length; i++)
            {
                stream.Write(bytes, i, 1);
                Thread.Sleep(1);
            }
        }

        private static void CheckFrame(DctPacket actual, DctPacket expected, string message)
        {
            byte[] received = actual.Encode(), sent = expected.Encode();
            Check(received.Length == sent.Length, message + " length");
            for (int i = 0; i < sent.Length; i++) Check(received[i] == sent[i], message + " byte " + i);
        }

        private static void ConfigureCurrentApp(NetworkStream stream, byte mode)
        {
            Check(Request(stream, 0x00).CommandId == 0x80, "Connect ACK");
            Check(Request(stream, 0x01).CommandId == 0x81, "Version response");
            Check(Request(stream, 0x09, 0).Payload[0] == 0, "Save interval query");
            Check(Request(stream, 0x09, 3).Payload[0] == 3, "Hardware environment query");
            Check(Request(stream, 0x09, 6, 0).Payload[0] == 6, "CAN mode ACK");
            var sm = Request(stream, 0x12, 1, 0, 0, 0, 0, 0);
            Check(sm.CommandId == 0x92 && sm.Payload.Length == 2 && sm.Payload[1] == 0,
                "No-sensor response count is zero, not a failure status");
            Check(Request(stream, 0x12, 1, 1, 0xFF, 0, 0, 0).Payload[1] == 1, "Enabled SM1 count");
            var channels = Request(stream, 0x12, 2, 0);
            Check(channels.Payload.Length == 3 && channels.Payload[0] == 2 && channels.Payload[1] == 0 &&
                channels.Payload[2] == 8, "SM channel query subtype/index/count");
            Request(stream, 0x12, 1, 0, 0, 0, 0, 0);
            Check(Request(stream, 0x03).Payload.Length == 6, "Hardware ID length");
            Check(Request(stream, 0x04, 12, 0, 0, 7, 0xEA, 10, 27, 0x20).Payload[0] == 1, "Time ACK");
            Request(stream, 0x06, 3, 49, 50, 51, 2);
            Request(stream, 0x08, 0, 4, 49, 48, 109, 98);
            if (mode == 1)
            {
                Check(Request(stream, 0x40, 1).Payload[0] == 1, "XCP USE");
                Check(Request(stream, 0x41, 0, 0x90, 6, 0, 0, 0x93, 6, 0, 0).Payload[0] == 1, "XCP IF_DATA");
                Check(Request(stream, 0x42, 0, 1, 2, 0, 0x10, 0, 0x70).Payload[0] == 1, "XCP measurements");
            }
            else if (mode == 0)
            {
                Request(stream, 0x10, 1, 0, 0xA0, 0, 1, 0, 1, 1);
                Request(stream, 0x13, 1, 0xA0, 1, 1);
            }
            else Check(Request(stream, 0x40, 2).Payload[0] == 1, "CAN-only XCP disabled");
            Request(stream, 0x11, 0, 0, 0);
            // Android does not wait for 97. Drain the optional legacy server reply in this fixture.
            Request(stream, 0x17, 0x31);
            Request(stream, 0x09, 0); Request(stream, 0x09, 3);
            Request(stream, 0x09, 6, 0); Request(stream, 0x12, 1, 0, 0, 0, 0, 0);
        }
        private static void VerifySlowReaderRecovery()
        {
            var listener = new TcpListener(IPAddress.Loopback, 0);
            listener.Start();
            ClientSession session = null;
            using (var peer = new TcpClient())
            {
                peer.ReceiveBufferSize = 65536;
                try
                {
                    peer.Connect(IPAddress.Loopback, ((IPEndPoint)listener.LocalEndpoint).Port);
                    var sender = listener.AcceptTcpClient();
                    sender.SendBufferSize = 4096;
                    session = new ClientSession(sender, "slow-reader");
                    int failures = 0;
                    session.SendFailed += (s, e) => { Interlocked.Increment(ref failures); Console.WriteLine(e); };
                    session.SetStreaming(true);
                    var bytes = new byte[4 * 1024 * 1024];
                    for (int i = 0; i < bytes.Length; i++) bytes[i] = (byte)(i % 251);
                    for (int chunk = 0; chunk < 16; chunk++)
                        Check(session.TryQueueTelemetry(bytes), "Queue slow-reader payload");
                    Thread.Sleep(1800);
                    Check(failures == 0 && session.SentPackets < 16, "A blocked write must survive the former 1s timeout; failures=" + failures + ", sent=" + session.SentPackets);
                    var stream = peer.GetStream();
                    stream.ReadTimeout = 5000;
                    var buffer = new byte[65536];
                    int received = 0;
                    while (received < bytes.Length * 16)
                    {
                        int n = stream.Read(buffer, 0, Math.Min(buffer.Length, bytes.Length * 16 - received));
                        Check(n > 0, "Connection must remain open after reader resumes");
                        for (int i = 0; i < n; i++) Check(buffer[i] == bytes[(received + i) % bytes.Length], "Byte order preserved after stall");
                        received += n;
                    }
                    Check(SpinWait.SpinUntil(() => session.SentPackets == 16, 2000), "Pending write must complete after recovery");
                    Check(session.SendControl(new byte[] { 0x20 }, 2000), "Control write after recovery");
                    Check(stream.ReadByte() == 0x20 && failures == 0, "Control traffic remains usable");
                    Console.WriteLine("PASS: 1.8s stalled reader recovers without disconnect, loss or duplication");
                }
                finally { if (session != null) session.Dispose(); listener.Stop(); }
            }
        }

        private static void VerifyQueuedControlSurvivesStall()
        {
            var listener = new TcpListener(IPAddress.Loopback, 0);
            listener.Start();
            ClientSession session = null;
            try
            {
                using (var peer = new TcpClient())
                {
                    peer.ReceiveBufferSize = 4096;
                    peer.Connect(IPAddress.Loopback, ((IPEndPoint)listener.LocalEndpoint).Port);
                    var sender = listener.AcceptTcpClient();
                    sender.SendBufferSize = 4096;
                    session = new ClientSession(sender, "control-stall");
                    session.SetStreaming(true);
                    var block = new byte[1024 * 1024];
                    session.TryQueueTelemetry(block);
                    Thread.Sleep(150);
                    var completed = new TaskCompletionSource<bool>();
                    Check(session.QueueControl(new byte[] { 0x77 }, sent => completed.TrySetResult(sent)), "Queue control");
                    Thread.Sleep(2800);
                    Check(!completed.Task.IsCompleted, "Control must remain pending behind stalled write");
                    var stream = peer.GetStream();
                    stream.ReadTimeout = 5000;
                    var buffer = new byte[65536];
                    int total = 0;
                    while (total < block.Length)
                    {
                        int count = stream.Read(buffer, 0, Math.Min(buffer.Length, block.Length - total));
                        Check(count > 0, "Stalled stream remains connected");
                        total += count;
                    }
                    Check(stream.ReadByte() == 0x77 && completed.Task.Wait(2000) && completed.Task.Result,
                        "Control must be delivered after the former 2.5s expiry");
                    int previousGeneration = session.TelemetryGeneration;
                    session.SetStreaming(false);
                    session.SetStreaming(true);
                    Check(!session.SendLogAsync(0xA3, new byte[] { 1 }, previousGeneration, CancellationToken.None).Result.HasValue,
                        "Previous run must not leak after restart");
                    session.Dispose();
                    Check(!session.SendLogAsync(0xA3, new byte[] { 1 }, session.TelemetryGeneration, CancellationToken.None).Result.HasValue,
                        "Disconnected file send must not wait forever");
                }
            }
            finally { if (session != null) session.Dispose(); listener.Stop(); }
            Console.WriteLine("PASS: delayed control delivery, old-run isolation, disconnect cancellation");
        }

        public static void Run()
        {
            RunCurrentAppCompatibility();
            VerifyApListener();
            VerifySlowReaderRecovery();
            VerifyQueuedControlSurvivesStall();
            var clock = new LogPlaybackClock();
            clock.Reset(0);
            clock.Advance(100, 1, false);
            Check(clock.DelayUntil(300, 2) == 100, "2x playback interval");
            clock.Advance(1100, 2, true);
            Check(clock.PositionMilliseconds == 100, "Pause must freeze source time");
            clock.Advance(1200, 2, false);
            Check(clock.PositionMilliseconds == 300, "Resume at changed speed");
            clock.Reset(1200);
            Check(clock.PositionMilliseconds == 0, "Restart/loop must reset source time");

            string fixture = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString("N") + ".txt");
            try
            {
                string hex = BitConverter.ToString(DctPacket.Create(0xA3, new byte[] { 1, 164, 1 }).Encode()).Replace('-', ' ');
                File.WriteAllLines(fixture, new[] { "[Recv][23:59:59.900] " + hex,
                    "[Recv][00:00:00.100] " + hex, "[Recv][00:00:03.100] " + hex });
                var log = new LogFileReader().Load(fixture);
                Check(log.Success && log.Packets.Count == 3, "Midnight log parsing");
                Check(log.Packets[1].LogElapsedMilliseconds == 200, "Midnight rollover");
                Check(log.Packets[2].LogElapsedMilliseconds == 3200, "Original log gap preserved");
            }
            finally { File.Delete(fixture); }

            var session = new ClientSession(new TcpClient(), "window-test");
            session.SetStreaming(true);
            for (int i = 0; i < ClientSession.TelemetryAckWindowSize; i++)
                Check(session.ReserveTelemetry(0xA3), "Reserve window");
            var blocked = Task.Run(() => session.ReserveTelemetry(0xA3));
            Check(!blocked.Wait(50), "Full ACK window must backpressure producer");
            session.Acknowledge(0x23);
            Check(blocked.Wait(1000) && blocked.Result, "ACK must release producer");
            blocked = Task.Run(() => session.ReserveTelemetry(0xA3));
            session.SetStreaming(false);
            Check(blocked.Wait(1000) && !blocked.Result, "STOP must release producer without sending");
            session.Client.Close();

            // A stalled ACK window must recover by retiring stale reservations;
            // it is never allowed to throw and close the transport session.
            var stalled = new ClientSession(new TcpClient(), "stall-test");
            stalled.SetStreaming(true);
            for (int i = 0; i < ClientSession.TelemetryAckWindowSize; i++)
                Check(stalled.ReserveTelemetry(0xA3), "Stall window fill");
            Thread.Sleep(3200);
            Check(stalled.ReserveTelemetry(0xA3), "Stalled ACKs must not disconnect or throw");
            stalled.SetStreaming(false);
            stalled.ResetTelemetryAcks();
            stalled.Client.Close();

            var server = new DctTcpServer();
            Check(server.Start(0), "Test protocol listener");
            var listener = (TcpListener)typeof(DctTcpServer).GetField("_listener", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(server);
            try
            {
                using (var client = new TcpClient())
                {
                    client.Connect(IPAddress.Loopback, ((IPEndPoint)listener.LocalEndpoint).Port);
                    var stream = client.GetStream();
                    stream.ReadTimeout = 3000;
                    Check(Request(stream, 0x20, 3).Payload[0] == 2, "START before handshake must fail");
                    Request(stream, 0x00); Request(stream, 0x01); Request(stream, 0x03); Request(stream, 0x04);
                    Check(Request(stream, 0x20, 3).Payload[0] == 2, "START before configuration must fail");
                    Request(stream, 0x09, 6, 0); Request(stream, 0x10, 0, 0);
                    Request(stream, 0x11, 0, 0); Request(stream, 0x13, 0, 0);
                    Check(Request(stream, 0x20, 3).Payload[0] == 1, "Configured START must succeed");
                    Check(SpinWait.SpinUntil(() => { foreach (var c in server.ActiveClients) if (c.Streaming) return true; return false; }, 1000), "Streaming activation");
                    server.BroadcastPacket(DctPacket.Create(0xA3, new byte[] { 1, 164, 7 }));
                    Check(Receive(stream).CommandId == 0xA3, "Telemetry after START");
                    byte[] ack = DctPacket.Create(0x23, new byte[] { 0 }).Encode(); // Valid NACK must retire pending frame too.
                    stream.Write(ack, 0, ack.Length);
                    // Lossless file replay must wait beyond the old 250 ms
                    // admission budget, not advance to the next record.
                    var replay = Task.Run(async () =>
                    {
                        for (int i = 0; i < 16; i++)
                            await server.BroadcastLogPacketAsync(DctPacket.Create(0xA3,
                                new byte[] { 1, 164, (byte)i }), i, CancellationToken.None);
                    });
                    Thread.Sleep(650);
                    Check(!replay.IsCompleted, "File replay must backpressure rather than skip records");
                    for (int i = 0; i < 16; i++)
                    {
                        var fileFrame = Receive(stream);
                        Check(fileFrame.CommandId == 0xA3 && fileFrame.Payload[2] == i,
                            "File record missing, duplicated or reordered: " + i);
                        stream.Write(ack, 0, ack.Length);
                    }
                    Check(replay.Wait(3000), "File replay resumes after ACKs");
                    Check(Request(stream, 0x21).CommandId == 0xA1, "STOP after backpressured file replay");
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "Restart after file replay");

                    // Do not ACK the next frame for longer than the old 3 s
                    // watchdog.  The server must retire the stale reservation,
                    // send the next frame, and keep the TCP session alive.
                    server.BroadcastPacket(DctPacket.Create(0xA3, new byte[] { 1, 164, 9 }));
                    Check(Receive(stream).CommandId == 0xA3, "Telemetry before delayed ACK");
                    Thread.Sleep(3200);
                    server.BroadcastPacket(DctPacket.Create(0xA3, new byte[] { 1, 164, 10 }));
                    Check(Receive(stream).CommandId == 0xA3, "Telemetry after delayed ACK");
                    Check(client.Client.Connected, "Delayed ACK must not close TCP session");
                    stream.Write(ack, 0, ack.Length);
                    Check(Request(stream, 0x21).CommandId == 0xA1, "STOP ACK");
                    server.BroadcastPacket(DctPacket.Create(0xA3, new byte[] { 1, 164, 8 }));
                    Check(!stream.DataAvailable, "No telemetry after STOP ACK");
                    Check(Request(stream, 0x20, 3).Payload[0] == 1, "Restart without reconnect");
                    Check(SpinWait.SpinUntil(() => { foreach (var c in server.ActiveClients) if (c.Streaming) return true; return false; }, 1000),
                        "Streaming reactivation on the existing session");
                    server.BroadcastPacket(DctPacket.Create(0xA3, new byte[] { 1, 164, 11 }));
                    var restartedFrame = Receive(stream);
                    Check(restartedFrame.CommandId == 0xA3 && restartedFrame.Payload[2] == 11,
                        "Telemetry must resume on the same TCP connection after STOP then START");
                    stream.Write(ack, 0, ack.Length);
                }

                // PC A2L-only setup flow: no MDB 0x10/0x13 is sent.
                // XCP USE -> IF_DATA -> MEASUREMENTS followed by common CAN
                // configuration must therefore be sufficient for START.
                using (var xcpClient = new TcpClient())
                {
                    xcpClient.Connect(IPAddress.Loopback, ((IPEndPoint)listener.LocalEndpoint).Port);
                    var stream = xcpClient.GetStream();
                    stream.ReadTimeout = 3000;
                    Request(stream, 0x00); Request(stream, 0x01); Request(stream, 0x03); Request(stream, 0x04);
                    Check(Request(stream, 0x40, 0x01).Payload[0] == 1, "XCP USE must succeed");
                    Check(Request(stream, 0x42, 0x00, 0x01, 0x02, 0x00, 0x10, 0x00, 0x70).Payload[0] == 0,
                        "XCP measurements before IF_DATA must fail");
                    Check(Request(stream, 0x41, 0x00, 0x90, 0x06, 0x00, 0x00, 0x93, 0x06, 0x00, 0x00).Payload[0] == 1,
                        "XCP IF_DATA must succeed");
                    Check(Request(stream, 0x42, 0x00, 0x01, 0x02, 0x00, 0x10, 0x00, 0x70).Payload[0] == 1,
                        "XCP measurements must succeed after IF_DATA");
                    Request(stream, 0x09, 0x06, 0x00);
                    Request(stream, 0x11, 0x00, 0x00);
                    Check(Request(stream, 0x20, 0x01).Payload[0] == 1,
                        "PC A2L-only configuration must allow START without MDB commands");
                    Check(Request(stream, 0x21).CommandId == 0xA1, "XCP STOP ACK");
                }
            }
            finally { server.Stop(); }
            Console.WriteLine("PASS: log timestamps/midnight/pause/speed/reset, ACK backpressure, MDB and PC A2L-only start/stop TCP exchange");
        }

        private static void VerifyApListener()
        {
            var server = new DctTcpServer();
            Check(!server.StartAp("invalid", 6000), "Invalid AP address must fail");
            Check(!server.StartAp("::1", 6000), "IPv6 AP address must fail");
            Check(!server.StartAp("0.0.0.0", 6000), "Wildcard AP address must fail");
            Check(!server.StartAp("127.0.0.1", 0) && !server.StartAp("127.0.0.1", 65536), "Out of range AP ports must fail");
            var start = typeof(DctTcpServer).GetMethod("Start", BindingFlags.Instance | BindingFlags.NonPublic,
                null, new[] { typeof(int), typeof(IPAddress), typeof(bool) }, null);
            var occupied = new TcpListener(IPAddress.Loopback, 0);
            occupied.Start();
            int occupiedPort = ((IPEndPoint)occupied.LocalEndpoint).Port;
            try {
                Check(!server.StartAp("127.0.0.1", occupiedPort), "AP occupied port must fail");
                Check(!server.IsRunning, "Failed AP listener must stay stopped");
            } finally { occupied.Stop(); }
            Check((bool)start.Invoke(server, new object[] { 0, IPAddress.Loopback, false }), "AP scoped listener after failure");
            try {
                var listener = (TcpListener)typeof(DctTcpServer).GetField("_listener", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(server);
                var endpoint = (IPEndPoint)listener.LocalEndpoint;
                Check(endpoint.Address.Equals(IPAddress.Loopback), "AP listener must bind the requested address");
                using (var client = new TcpClient()) {
                    client.Connect(endpoint);
                    var stream = client.GetStream();
                    stream.ReadTimeout = 3000;
                    Check(Request(stream, 0x00).CommandId == 0x80, "AP handshake ENABLE");
                    Check(Request(stream, 0x01).CommandId == 0x81, "AP handshake VERSION");
                    Request(stream, 0x03); Request(stream, 0x04);
                    Request(stream, 0x09, 6, 0); Request(stream, 0x10, 0, 0);
                    Request(stream, 0x11, 0, 0); Request(stream, 0x13, 0, 0);
                    Check(Request(stream, 0x20, 1).Payload[0] == 1, "AP configured START");
                    Check(SpinWait.SpinUntil(() => { foreach (var c in server.ActiveClients) if (c.Streaming) return true; return false; }, 1000), "AP streaming activation");
                    server.BroadcastPacket(DctPacket.Create(0xA3, new byte[] { 1, 164, 7 }));
                    Check(Receive(stream).CommandId == 0xA3, "AP telemetry");
                    Check(Request(stream, 0x21).CommandId == 0xA1, "AP STOP ACK");
                }
            } finally { server.Stop(); }
            Check(server.Start(0), "Direct listener must still start after AP stop");
            server.Stop();
            Console.WriteLine("PASS: AP scoped TCP handshake/configuration/telemetry/STOP, bind failure cleanup, Direct restart");
        }
    }
}