Simulate Kestrel slab transport for SignalR BWO tests

Add a production-faithful test harness for SignalR binary protocol, introducing SlabTransportWriter to simulate Kestrel's slab allocator and always force the BufferWriterOutput owned-buffer path. Add large-payload round-trip tests (including non-ASCII cases) to catch position drift and data corruption bugs. Enhance protocol tests to validate multi-segment output and byte-for-byte correctness. All protocol round-trips now exercise the multi-segment, non-array-backed buffer path.

AyCode.Services.Server.Tests/SignalRs/SignalRClientToHubTest.cs

@@ -1069,6 +1069,125 @@ public abstract class SignalRClientToHubTestBase
         }
     }
 
+    /// <summary>
+    /// 250KB+ payload with ASCII-only strings.
+    /// Validates BWO owned-buffer path with many Grow cycles.
+    /// </summary>
+    [TestMethod]
+    public async Task RoundTrip_VeryLargeOrderList_250KB_PreservesAllData()
+    {
+        TestDataFactory.ResetIdCounter();
+        var orders = new List<TestOrder>();
+        for (var i = 0; i < 100; i++)
+        {
+            var tag = TestDataFactory.CreateTag($"Tag_{i}");
+            var user = TestDataFactory.CreateUser($"user_{i}");
+            orders.Add(TestDataFactory.CreateOrder(
+                itemCount: 5,
+                palletsPerItem: 3,
+                measurementsPerPallet: 3,
+                pointsPerMeasurement: 5,
+                sharedTag: tag,
+                sharedUser: user));
+        }
+
+        var result = await _client.PostDataAsync<List<TestOrder>, List<TestOrder>>(
+            TestSignalRTags.TestOrderListParam, orders);
+
+        Assert.IsNotNull(result, "Deserialization returned null — likely BWO GetTotalPosition drift on large payload");
+        Assert.AreEqual(orders.Count, result.Count, "Order count mismatch");
+        for (var i = 0; i < orders.Count; i++)
+        {
+            Assert.AreEqual(orders[i].Id, result[i].Id, $"Order[{i}].Id mismatch");
+            Assert.AreEqual(orders[i].Items.Count, result[i].Items.Count, $"Order[{i}].Items.Count mismatch");
+        }
+    }
+
+    /// <summary>
+    /// Large payload with non-ASCII (Hungarian) strings — targets the WriteStringUtf8
+    /// savedPosition bug that causes BWO GetTotalPosition drift when a non-ASCII string
+    /// straddles a chunk boundary and Grow resets _position.
+    ///
+    /// Production evidence: Array=44111, BWO_pipe=56340, BWO_temp=44111
+    /// The bug only manifests when TryGetArray fails (MemoryManager-backed Memory)
+    /// AND non-ASCII strings trigger the UTF-8 fallback with savedPosition rewind.
+    /// </summary>
+    [TestMethod]
+    public async Task RoundTrip_LargeOrderList_NonAsciiStrings_PreservesAllData()
+    {
+        // Non-ASCII strings that trigger UTF-8 fallback in WriteStringUtf8
+        var hungarianNames = new[]
+        {
+            "Kürtőskalács Értékesítő Kft.",
+            "Széchenyi István Tér",
+            "Büfé és Étkezde Zrt.",
+            "Különleges Árú Raktár",
+            "Möbius Szállítmányozás",
+            "Tündérkert Óvoda és Bölcsőde",
+            "Győri Főpályaudvar",
+            "Hősök Tere Múzeum",
+            "Péterfy Sándor Utcai Kórház",
+            "Közgondnokság Ügyfélfogadó"
+        };
+
+        TestDataFactory.ResetIdCounter();
+        var orders = new List<TestOrder>();
+        for (var i = 0; i < 80; i++)
+        {
+            var tag = TestDataFactory.CreateTag($"Cég_{i}_{hungarianNames[i % hungarianNames.Length]}");
+            var user = TestDataFactory.CreateUser($"felhasználó_{i}");
+            user.FirstName = hungarianNames[i % hungarianNames.Length];
+            user.LastName = hungarianNames[(i + 3) % hungarianNames.Length];
+            user.Email = $"felhasználó_{i}@székesfehérvár.hu";
+            user.Username = $"ügyfél_{hungarianNames[(i + 5) % hungarianNames.Length]}";
+
+            var order = TestDataFactory.CreateOrder(
+                itemCount: 4,
+                palletsPerItem: 3,
+                measurementsPerPallet: 3,
+                pointsPerMeasurement: 4,
+                sharedTag: tag,
+                sharedUser: user);
+
+            // Inject non-ASCII product names to maximize chunk-boundary collisions
+            foreach (var item in order.Items)
+            {
+                item.ProductName = $"Termék_{hungarianNames[(i + item.Id) % hungarianNames.Length]}_{i}";
+            }
+
+            order.OrderNumber = $"RND-{i:D4}-{hungarianNames[i % hungarianNames.Length]}";
+            orders.Add(order);
+        }
+
+        var result = await _client.PostDataAsync<List<TestOrder>, List<TestOrder>>(
+            TestSignalRTags.TestOrderListParam, orders);
+
+        Assert.IsNotNull(result,
+            "Deserialization returned null — BWO savedPosition drift on non-ASCII strings at chunk boundary");
+        Assert.AreEqual(orders.Count, result.Count, "Order count mismatch");
+        for (var i = 0; i < orders.Count; i++)
+        {
+            Assert.AreEqual(orders[i].Id, result[i].Id, $"Order[{i}].Id mismatch");
+            Assert.AreEqual(orders[i].OrderNumber, result[i].OrderNumber, $"Order[{i}].OrderNumber mismatch");
+            Assert.AreEqual(orders[i].Items.Count, result[i].Items.Count, $"Order[{i}].Items.Count mismatch");
+            for (var j = 0; j < orders[i].Items.Count; j++)
+            {
+                Assert.AreEqual(orders[i].Items[j].ProductName, result[i].Items[j].ProductName,
+                    $"Order[{i}].Items[{j}].ProductName mismatch — non-ASCII string corrupted");
+            }
+        }
+    }
+
+    /// <summary>
+    /// Sanity check: SlabTransportWriter.GetMemory returns MemoryManager-backed Memory
+    /// so TryGetArray fails, forcing BWO into the owned-buffer code path.
+    /// </summary>
+    [TestMethod]
+    public void SlabTransportWriter_GetMemory_TryGetArrayFails()
+    {
+        SlabTransportWriter.VerifyMemoryManagerBacked();
+    }
+
     #endregion
 }
 

AyCode.Services.Server.Tests/SignalRs/SlabTransportWriter.cs

@@ -0,0 +1,215 @@
+using System.Buffers;
+using System.Runtime.InteropServices;
+
+namespace AyCode.Services.Server.Tests.SignalRs;
+
+/// <summary>
+/// Custom IBufferWriter that simulates Kestrel's PinnedBlockMemoryPool transport behavior:
+///
+/// Production: Kestrel PipeWriter → PinnedBlockMemoryPool → MemoryManager-backed Memory
+///             → TryGetArray FAILS → BWO takes owned-buffer fallback path
+///
+/// Test:       SlabTransportWriter → SlabMemoryManager-backed Memory
+///             → TryGetArray FAILS → BWO takes owned-buffer fallback path (same as production)
+///
+/// Key behaviors:
+/// - GetMemory returns MemoryManager-backed Memory (TryGetArray always fails)
+/// - Fixed-size slab segments with random offsets (simulates slab allocator)
+/// - After Advance, remaining slab space is reused (offset grows)
+/// - GetMemory may return less than sizeHint (remaining slab space)
+/// - Deterministic via seeded Random for reproducible tests
+/// </summary>
+internal sealed class SlabTransportWriter : IBufferWriter<byte>
+{
+    private readonly int _slabSize;
+    private readonly Random _rng;
+
+    // Committed data tracking
+    private readonly List<CommittedSegment> _segments = new();
+    private int _totalCommitted;
+
+    // Current slab state
+    private byte[]? _currentSlab;
+    private int _writePos;   // current write position within slab
+    private int _slabEnd;    // end of usable area in slab
+
+    public SlabTransportWriter(int slabSize = 256, int seed = 42)
+    {
+        _slabSize = slabSize;
+        _rng = new Random(seed);
+    }
+
+    /// <summary>Total bytes committed via Advance.</summary>
+    public int WrittenCount => _totalCommitted;
+
+    /// <summary>Number of slab segments allocated.</summary>
+    public int SlabCount { get; private set; }
+
+    public void Advance(int count)
+    {
+        if (_currentSlab == null)
+            throw new InvalidOperationException("Call GetMemory/GetSpan before Advance");
+        if (count < 0 || _writePos + count > _slabEnd)
+            throw new InvalidOperationException(
+                $"Advance({count}) invalid: writePos={_writePos}, slabEnd={_slabEnd}, remaining={_slabEnd - _writePos}");
+
+        _segments.Add(new CommittedSegment(_currentSlab, _writePos, count));
+        _writePos += count;
+        _totalCommitted += count;
+    }
+
+    /// <summary>
+    /// Returns MemoryManager-backed Memory so that TryGetArray ALWAYS fails.
+    /// May return fewer bytes than sizeHint (remaining slab space) — legal per IBufferWriter contract.
+    /// This forces BWO to rent from ArrayPool (owned-buffer path), matching production behavior.
+    /// </summary>
+    public Memory<byte> GetMemory(int sizeHint = 0)
+    {
+        sizeHint = Math.Max(1, sizeHint);
+        var remaining = _currentSlab != null ? _slabEnd - _writePos : 0;
+
+        if (remaining <= 0)
+        {
+            // Allocate new slab — at least sizeHint to avoid starving the caller
+            AllocateNewSlab(Math.Max(sizeHint, _slabSize));
+            remaining = _slabEnd - _writePos;
+        }
+
+        // Return MemoryManager-backed Memory: TryGetArray will fail
+        return new SlabMemoryManager(_currentSlab!, _writePos, remaining).Memory;
+    }
+
+    /// <summary>
+    /// Returns Span with at least sizeHint bytes.
+    /// Used by FlushOwnedBuffer: _writer.GetSpan(bytesInChunk) must be large enough for CopyTo.
+    /// Allocates new slab if remaining space is insufficient.
+    /// </summary>
+    public Span<byte> GetSpan(int sizeHint = 0)
+    {
+        sizeHint = Math.Max(1, sizeHint);
+        var remaining = _currentSlab != null ? _slabEnd - _writePos : 0;
+
+        if (remaining < sizeHint)
+        {
+            AllocateNewSlab(Math.Max(sizeHint, _slabSize));
+            remaining = _slabEnd - _writePos;
+        }
+
+        return _currentSlab.AsSpan(_writePos, remaining);
+    }
+
+    private void AllocateNewSlab(int minSize)
+    {
+        // Random offset within slab — simulates Kestrel slab allocator non-zero offsets
+        var offset = _rng.Next(0, Math.Max(1, _slabSize / 4));
+        // ±12% size jitter for variety
+        var jitter = _rng.Next(-_slabSize / 8, _slabSize / 8 + 1);
+        var actualSize = Math.Max(minSize, _slabSize + jitter);
+        _currentSlab = new byte[actualSize + offset];
+        _writePos = offset;
+        _slabEnd = offset + actualSize;
+        SlabCount++;
+    }
+
+    /// <summary>
+    /// Get all committed bytes as a contiguous array.
+    /// </summary>
+    public byte[] ToArray()
+    {
+        var result = new byte[_totalCommitted];
+        var pos = 0;
+        foreach (var seg in _segments)
+        {
+            Buffer.BlockCopy(seg.Array, seg.Offset, result, pos, seg.Length);
+            pos += seg.Length;
+        }
+        return result;
+    }
+
+    /// <summary>
+    /// Build a multi-segment ReadOnlySequence from committed data, splitting at slab boundaries.
+    /// Each committed segment becomes a separate ReadOnlySequence segment.
+    /// </summary>
+    public ReadOnlySequence<byte> ToReadOnlySequence()
+    {
+        if (_segments.Count == 0)
+            return ReadOnlySequence<byte>.Empty;
+
+        if (_segments.Count == 1)
+        {
+            var seg = _segments[0];
+            return new ReadOnlySequence<byte>(seg.Array, seg.Offset, seg.Length);
+        }
+
+        // Build linked segment list
+        var first = new MemorySegment(new ReadOnlyMemory<byte>(_segments[0].Array, _segments[0].Offset, _segments[0].Length));
+        var current = first;
+        for (var i = 1; i < _segments.Count; i++)
+        {
+            var seg = _segments[i];
+            current = current.Append(new ReadOnlyMemory<byte>(seg.Array, seg.Offset, seg.Length));
+        }
+
+        return new ReadOnlySequence<byte>(first, 0, current, current.Memory.Length);
+    }
+
+    /// <summary>
+    /// Verify that TryGetArray fails on our Memory (sanity check for test correctness).
+    /// </summary>
+    public static void VerifyMemoryManagerBacked()
+    {
+        var writer = new SlabTransportWriter(64);
+        var mem = writer.GetMemory(16);
+        if (MemoryMarshal.TryGetArray(mem, out ArraySegment<byte> _))
+            throw new InvalidOperationException(
+                "SlabTransportWriter.GetMemory returned array-backed Memory — TryGetArray should fail!");
+    }
+
+    private record struct CommittedSegment(byte[] Array, int Offset, int Length);
+
+    /// <summary>
+    /// MemoryManager that wraps an array region but returns Memory where TryGetArray fails.
+    /// This is the key difference from production Kestrel PinnedBlockMemoryPool.
+    /// </summary>
+    private sealed class SlabMemoryManager : MemoryManager<byte>
+    {
+        private readonly byte[] _array;
+        private readonly int _offset;
+        private readonly int _length;
+
+        public SlabMemoryManager(byte[] array, int offset, int length)
+        {
+            _array = array;
+            _offset = offset;
+            _length = length;
+        }
+
+        public override Span<byte> GetSpan() => _array.AsSpan(_offset, _length);
+
+        public override MemoryHandle Pin(int elementIndex = 0)
+            => throw new NotSupportedException("SlabMemoryManager does not support pinning");
+
+        public override void Unpin()
+            => throw new NotSupportedException("SlabMemoryManager does not support pinning");
+
+        protected override void Dispose(bool disposing) { }
+    }
+
+    /// <summary>
+    /// ReadOnlySequenceSegment for building multi-segment sequences from committed data.
+    /// </summary>
+    private sealed class MemorySegment : ReadOnlySequenceSegment<byte>
+    {
+        public MemorySegment(ReadOnlyMemory<byte> memory)
+        {
+            Memory = memory;
+        }
+
+        public MemorySegment Append(ReadOnlyMemory<byte> memory)
+        {
+            var next = new MemorySegment(memory) { RunningIndex = RunningIndex + Memory.Length };
+            Next = next;
+            return next;
+        }
+    }
+}

AyCode.Services.Server.Tests/SignalRs/TestMultiSegmentProtocol.cs

@@ -8,13 +8,19 @@ using Microsoft.AspNetCore.SignalR.Protocol;
 namespace AyCode.Services.Server.Tests.SignalRs;
 
 /// <summary>
-/// Test protocol that simulates production Kestrel pipe behavior with 256-byte segments.
+/// Test protocol that simulates production Kestrel transport behavior:
 ///
-/// Production: SignalR → WriteMessage(PipeWriter) → Kestrel slab 4096-byte segments → PipeReader → TryParseMessage
-/// Test:       SignalR → WriteMessage(PipeWriter) → FixedSizePool 256-byte segments → PipeReader → TryParseMessage
+/// WRITE SIDE (GetMessageBytesMultiSegment):
+///   WriteMessage → SlabTransportWriter (MemoryManager-backed, TryGetArray fails)
+///   → BWO takes owned-buffer fallback path (same as production Kestrel PipeWriter)
+///   → Automatic byte-by-byte comparison against ArrayBufferWriter reference
 ///
-/// Both sides go through a real Pipe with fixed-size memory segments,
-/// exercising BWO chunk writes and SequenceBinaryInput cross-boundary reads.
+/// READ SIDE (TryParseMessage):
+///   Bytes → Pipe(SlabSimulatingPool, 256B segments) → multi-segment ReadOnlySequence
+///   → SequenceBinaryInput cross-boundary reads (same as production Kestrel PipeReader)
+///
+/// Production: SignalR → WriteMessage(PipeWriter/Kestrel) → 4096B slab segments → TryParseMessage
+/// Test:       SignalR → WriteMessage(SlabTransportWriter) → 256B slab segments → TryParseMessage
 /// </summary>
 internal class TestMultiSegmentProtocol : AyCodeBinaryHubProtocol
 {
@@ -26,23 +32,35 @@ internal class TestMultiSegmentProtocol : AyCodeBinaryHubProtocol
     }
 
     /// <summary>
-    /// Write side: WriteMessage → PipeWriter backed by 256-byte pool segments.
-    /// Same code path as production, just smaller segments.
+    /// Write side: WriteMessage → SlabTransportWriter (MemoryManager-backed Memory).
+    /// Forces BWO into owned-buffer fallback path — same code path as production Kestrel.
+    /// Validates output against ArrayBufferWriter reference on every call.
     /// </summary>
-    public new ReadOnlyMemory<byte> GetMessageBytes(HubMessage message)
+    public ReadOnlyMemory<byte> GetMessageBytesMultiSegment(HubMessage message)
     {
-        var pipe = new Pipe(new PipeOptions(pool: new SlabSimulatingPool(SegmentSize)));
-        WriteMessage(message, pipe.Writer);
-        pipe.Writer.Complete();
-        pipe.Reader.TryRead(out var result);
-        var bytes = result.Buffer.ToArray();
-        pipe.Reader.Complete();
-        return bytes;
+        // ── Transport-double path (production simulation) ──────────────────
+        var transport = new SlabTransportWriter(SegmentSize);
+        WriteMessage(message, transport);
+        var transportBytes = transport.ToArray();
+
+        // ── Reference path: ArrayBufferWriter with large capacity (no resize → lengthSpan stays valid) ──
+        // NOTE: base.GetMessageBytes uses capacity = chunkSize + 4 = 260, which causes resize
+        //       on any non-trivial message → invalidates the back-patched lengthSpan.
+        //       We use a large capacity to ensure no resize ever happens.
+        var referenceCapacity = Math.Max(transportBytes.Length + 256, 65536);
+        var reference = new ArrayBufferWriter<byte>(referenceCapacity);
+        WriteMessage(message, reference);
+        var referenceBytes = reference.WrittenSpan;
+
+        // ── Validate: transport output must match reference byte-for-byte ──
+        ValidateAgainstReference(transportBytes, referenceBytes);
+
+        return transportBytes;
     }
 
     /// <summary>
-    /// Read side: fill PipeWriter 256 bytes at a time → PipeReader gives multi-segment sequence.
-    /// Same as production Kestrel PipeReader delivering 4096-byte segments.
+    /// Read side: fill Pipe with 256-byte slab segments → multi-segment ReadOnlySequence.
+    /// Same as production Kestrel PipeReader delivering slab-sized segments.
     /// </summary>
     public override bool TryParseMessage(ref ReadOnlySequence<byte> input, IInvocationBinder binder,
         [NotNullWhen(true)] out HubMessage? message)
@@ -65,11 +83,98 @@ internal class TestMultiSegmentProtocol : AyCodeBinaryHubProtocol
         writer.Complete();
         pipe.Reader.TryRead(out var result);
         var seq = result.Buffer;
+
+        // Assert multi-segment: if payload > SegmentSize, sequence must NOT be single-segment
+        if (bytes.Length > SegmentSize)
+        {
+            AssertMultiSegment(seq, bytes.Length);
+        }
+
         var success = base.TryParseMessage(ref seq, binder, out message);
         pipe.Reader.Complete();
         return success;
     }
 
+    #region Validation
+
+    /// <summary>
+    /// Byte-by-byte comparison of transport-double output vs ArrayBufferWriter reference.
+    /// Catches any BWO owned-buffer path bug (position drift, data corruption, length mismatch).
+    /// </summary>
+    private static void ValidateAgainstReference(byte[] transportBytes, ReadOnlySpan<byte> referenceBytes)
+    {
+        var refArray = referenceBytes.ToArray();
+
+        // ── Total byte count ──
+        if (transportBytes.Length != refArray.Length)
+        {
+            // Also check outer length prefix for diagnostics
+            var transportPrefix = transportBytes.Length >= 4 ? BitConverter.ToInt32(transportBytes, 0) : -1;
+            var referencePrefix = refArray.Length >= 4 ? BitConverter.ToInt32(refArray, 0) : -1;
+
+            throw new InvalidOperationException(
+                $"[TRANSPORT_DOUBLE] Total byte count mismatch: transport={transportBytes.Length}, reference={refArray.Length}. " +
+                $"Diff={transportBytes.Length - refArray.Length} bytes. " +
+                $"Outer length prefix: transport={transportPrefix}, reference={referencePrefix}. " +
+                $"BWO GetTotalPosition drift detected.");
+        }
+
+        // ── Outer length prefix check (first 4 bytes) ──
+        if (transportBytes.Length >= 4)
+        {
+            var transportPrefix = BitConverter.ToInt32(transportBytes, 0);
+            var referencePrefix = BitConverter.ToInt32(refArray, 0);
+            if (transportPrefix != referencePrefix)
+            {
+                throw new InvalidOperationException(
+                    $"[TRANSPORT_DOUBLE] Outer length prefix mismatch: transport={transportPrefix}, reference={referencePrefix}. " +
+                    $"Total bytes match ({transportBytes.Length}) but prefix differs. " +
+                    $"BWO owned-buffer path likely has position drift.");
+            }
+        }
+
+        // ── Byte-by-byte content ──
+        var minLen = Math.Min(transportBytes.Length, refArray.Length);
+        for (int i = 0; i < minLen; i++)
+        {
+            if (transportBytes[i] != refArray[i])
+            {
+                var start = Math.Max(0, i - 8);
+                var end = Math.Min(minLen, i + 16);
+                var refHex = Convert.ToHexString(refArray.AsSpan(start, end - start));
+                var trnHex = Convert.ToHexString(transportBytes.AsSpan(start, end - start));
+                throw new InvalidOperationException(
+                    $"[TRANSPORT_DOUBLE] Content mismatch at byte {i}/{minLen}: " +
+                    $"ref={refHex} transport={trnHex}. " +
+                    $"BWO owned-buffer path writing corrupt data.");
+            }
+        }
+    }
+
+    private static void AssertMultiSegment(ReadOnlySequence<byte> seq, int totalLength)
+    {
+        if (seq.IsSingleSegment)
+        {
+            throw new InvalidOperationException(
+                $"[MULTI_SEGMENT] Expected multi-segment sequence for {totalLength} bytes " +
+                $"(> {SegmentSize}B segment size), but got single segment. " +
+                $"SlabSimulatingPool or Pipe configuration is wrong.");
+        }
+
+        // Count segments
+        var segmentCount = 0;
+        foreach (var _ in seq)
+            segmentCount++;
+
+        if (segmentCount < 2)
+        {
+            throw new InvalidOperationException(
+                $"[MULTI_SEGMENT] Expected >= 2 segments for {totalLength} bytes, got {segmentCount}.");
+        }
+    }
+
+    #endregion
+
     /// <summary>
     /// MemoryPool that returns <paramref name="segmentSize"/>-byte blocks at random offsets
     /// within a larger backing array — simulating Kestrel's slab allocator where segments
@@ -85,8 +190,8 @@ internal class TestMultiSegmentProtocol : AyCodeBinaryHubProtocol
         {
             var size = Math.Max(minBufferSize, segmentSize);
             var offset = _rng.Next(0, segmentSize);       // random slab offset
-            var jitter = _rng.Next(-1, 2);                 // -1, 0, or +1
-            var actualSize = Math.Max(1, size + jitter);   // random segment size variance
+            var jitter = _rng.Next(-segmentSize / 4, segmentSize / 4 + 1); // ±25% size variance
+            var actualSize = Math.Max(16, size + jitter);
             var array = new byte[actualSize + offset];
             return new Owner(array, offset, actualSize);
         }

AyCode.Services.Server.Tests/SignalRs/TestableSignalRClient2.cs

@@ -65,7 +65,7 @@ public class TestableSignalRClient2 : AcSignalRClientBase, IAcSignalRHubItemServ
             nameof(IAcSignalRHubClient.OnReceiveMessage),
             [messageTag, requestId, signalParams, data ?? Array.Empty<byte>()]);
 
-        var bytes = _protocol.GetMessageBytes(invocation);
+        var bytes = _protocol.GetMessageBytesMultiSegment(invocation);
         var sequence = new ReadOnlySequence<byte>(bytes);
         if (!_protocol.TryParseMessage(ref sequence, _binder, out var parsed) || parsed is not InvocationMessage invMsg)
             throw new InvalidOperationException(

AyCode.Services.Server.Tests/SignalRs/TestableSignalRHub2.cs

@@ -122,7 +122,7 @@ public class TestableSignalRHub2 : AcWebSignalRHubBase<TestSignalRTags, TestLogg
             nameof(IAcSignalRHubClient.OnReceiveMessage),
             [messageTag, requestId, signalParams, responseData ?? Array.Empty<byte>()]);
 
-        var bytes = _protocol.GetMessageBytes(invocation);
+        var bytes = _protocol.GetMessageBytesMultiSegment(invocation);
         var sequence = new ReadOnlySequence<byte>(bytes);
         _protocol.TryParseMessage(ref sequence, _binder, out var parsed);