Dans ma boucle de réception, à un certain moment, la fonction 'Receive' de mon socket de réception, normalement bloquante, retourne directement en me renvoyant un nombre de bytes inférieur à celui demandé.  

Ce nombre est toujours soit 404 soit 0. Dans le cas où je reçois 0 byte, ma connexion est irrécupérable et la fonction Receive me retournera toujours 0.
Par contre, lorsque je reçois 404 bytes, je reçois parfois les suivants au Receive suivant...  
 

J'ai l'impression que ce phénomène est du à un débordement du buffer de réception lorsque windows prend la main trop longtemps. Est-ce possible?
Pourquoi la fonction Receive retourne simplement sans balancer d'exception?

Imports System.Net.Sockets
Imports System.Net
Imports System.Text
 
Public Class ClassComm
  Implements IDisposable
 
#Region "IDisposable Support"
  Private disposedValue As Boolean = False
 
  ' IDisposable
  Protected Overridable Sub Dispose(ByVal disposing As Boolean)
    If Not Me.disposedValue Then
      If disposing Then
        If Not TimerConnectionTimeOut Is Nothing Then
          TimerConnectionTimeOut.Enabled = False
          TimerConnectionTimeOut.Close()
          TimerConnectionTimeOut.Dispose()
          TimerConnectionTimeOut = Nothing
        End If
        If Not TimerSendTimeOut Is Nothing Then
          TimerSendTimeOut.Enabled = False
          TimerSendTimeOut.Close()
          TimerSendTimeOut.Dispose()
          TimerSendTimeOut = Nothing
        End If
        If Not TimerSend Is Nothing Then
          TimerSend.Enabled = False
          TimerSend.Close()
          TimerSend.Dispose()
          TimerSend = Nothing
        End If
        _bytes = Nothing
        _qrcv.Clear()
        _qrcv = Nothing
        _qsnd.Clear()
        _qsnd = Nothing
        On Error Resume Next
        _sck.Shutdown(SocketShutdown.Both)
        _sck.Close()
        On Error GoTo 0
        _sck = Nothing
      End If
      'free shared unmanaged resources
    End If
    Me.disposedValue = True
  End Sub
 
  Public Sub Dispose() Implements IDisposable.Dispose
    Dispose(True)
    GC.SuppressFinalize(Me)
  End Sub
#End Region
 
#Region "Enumeration"
  Public Enum ErrorType
    seems_disconnected
    connection_failed
    failed_to_listen
  End Enum
#End Region
 
#Region "Structure"
  Public Structure CommMessage
    Public Order As String
    Public Message As String
    Private _idCode As Long
    Public Property idCode() As Long
      Get
        If _idCode = 0 Then _idCode = Now.Ticks
        Return _idCode
      End Get
      Set(ByVal value As Long)
        If _idCode = 0 Then _idCode = value
      End Set
    End Property
    Public ReadOnly Property MyBytes() As Byte()
      Get
        If _idCode = 0 Then _idCode = Now.Ticks
        Dim ms As New IO.MemoryStream
        Dim bw As New IO.BinaryWriter(ms, Encoding.Unicode)
        With bw
          .Write(Order)
          .Write(Message)
          .Write(_idCode)
          .Close()
        End With
        ms.Close()
        Return ms.ToArray
        bw = Nothing
        ms.Dispose()
        ms = Nothing
      End Get
    End Property
    Public Sub SetBytes(ByRef ByteCommMessage As Byte())
      Dim ms As New IO.MemoryStream(ByteCommMessage, False)
      Dim br As New IO.BinaryReader(ms, Encoding.Unicode)
      With br
        Order = .ReadString
        Message = .ReadString
        _idCode = .ReadUInt64
        .Close()
      End With
      br = Nothing
      ms.Close()
      ms.Dispose()
      ms = Nothing
    End Sub
    Public Function ConfirmSequence() As Byte()
      Dim ms As New IO.MemoryStream
      Dim bw As New IO.BinaryWriter(ms, Encoding.Unicode)
      With bw
        .Write("" )
        .Write("" )
        .Write(_idCode)
        .Close()
      End With
      ms.Close()
      Return ms.ToArray
      bw = Nothing
      ms.Dispose()
      ms = Nothing
    End Function
  End Structure
#End Region
 
#Region "Private objects"
  Private _bytes() As Byte
  Private _qrcv As New Queue(Of CommMessage)
  Private _qsnd As New Queue(Of CommMessage)
  Private _last_send As CommMessage
  Private _last_rcv As CommMessage
  Private _sck As Socket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP)
  Private WithEvents TimerConnectionTimeOut As Timers.Timer
  Private WithEvents TimerSendTimeOut As Timers.Timer
  Private WithEvents TimerSend As New Timers.Timer(100)
  Private _sending As Boolean = False
#End Region
 
#Region "Events"
  Public Event ConnectionRequestAccepted(ByRef sck As Socket)
  Public Event Connected()
  Public Event ProblemDetected(ByVal source As ErrorType)
#End Region
 
#Region "Constructor New"
 
  Public Sub New(ByVal Port_To_Listen_If_Server As Integer)
    _last_rcv.idCode = -1
    Try
      With _sck
        .Bind(New IPEndPoint(IPAddress.Any, Port_To_Listen_If_Server))
        .Listen(10)
        .BeginAccept(AddressOf CallBackAccept, _sck)
      End With
    Catch
      RaiseEvent ProblemDetected(ErrorType.failed_to_listen)
    End Try
  End Sub
  Public Sub New(ByVal Host_To_Connect As String, ByVal Port_To_Connect As Integer, Optional ByVal Timeout_ms As Integer = 5000)
    _last_rcv.idCode = -1
    If Timeout_ms >= 0 Then
      TimerConnectionTimeOut = New Timers.Timer
      TimerConnectionTimeOut.Interval = Timeout_ms
      TimerConnectionTimeOut.Enabled = True
      TimerSendTimeOut = New Timers.Timer
      TimerSendTimeOut.Interval = Timeout_ms
      TimerSendTimeOut.Enabled = False
    End If
    Try
      _sck.BeginConnect(Host_To_Connect, Port_To_Connect, AddressOf CallBackConnect, _sck)
    Catch
      RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
    End Try
  End Sub
  Public Sub New(ByRef Sck As Socket, Optional ByVal Timeout_ms As Integer = 5000)
    _last_rcv.idCode = -1
    If Sck.Connected Then
      If Timeout_ms >= 0 Then
        TimerSendTimeOut = New Timers.Timer
        TimerSendTimeOut.Interval = Timeout_ms
        TimerSendTimeOut.Enabled = False
      End If
      Try
        _sck = Sck
        TimerSend.Enabled = True
        _bytes = New Byte(_sck.ReceiveBufferSize) {}
        _sck.BeginReceive(_bytes, 0, _sck.ReceiveBufferSize, SocketFlags.None, AddressOf CallBackReceive, _sck)
      Catch
        RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
      End Try
    Else
      RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
    End If
  End Sub
 
#End Region
 
#Region "Timers events"
  Private Sub TimerConnectionTimeOut_Elapsed(ByVal sender As Object, ByVal e As system.Timers.ElapsedEventArgs) Handles TimerConnectionTimeOut.Elapsed
    TimerConnectionTimeOut.Enabled = False
    RaiseEvent ProblemDetected(ErrorType.connection_failed)
  End Sub
 
  Private Sub TimerSendTimeOut_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles TimerSendTimeOut.Elapsed
    If _sending Then Sendcm(_last_send.MyBytes) Else TimerSendTimeOut.Enabled = False
  End Sub
 
  Private Sub TimerSend_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles TimerSend.Elapsed
    If Not _sending Then
      If _qsnd.Count > 0 Then
        Sending(True)
        _last_send = _qsnd.Dequeue
        Sendcm(_last_send.MyBytes)
      End If
    End If
  End Sub
 
#End Region
 
#Region "Public properties"
  Public ReadOnly Property ReadNextMsg() As CommMessage
    Get
      If _qrcv.Count > 0 Then Return _qrcv.Dequeue Else Return Nothing
    End Get
  End Property
 
  Public ReadOnly Property MsgCount() As Integer
    Get
      Return _qrcv.Count
    End Get
  End Property
#End Region
 
#Region "Public functions"
 
  Public Overloads Sub Send(ByVal Order As String, ByVal Message As String)
    Dim cm As New CommMessage
    cm.Order = Order
    cm.Message = Message
    _qsnd.Enqueue(cm)
  End Sub
  Public Overloads Sub Send(ByRef varCommMessage As CommMessage)
    _qsnd.Enqueue(varCommMessage)
  End Sub
  Public Overloads Sub Send(ByRef BytesCommMessage As Byte())
    Dim cm As New CommMessage
    cm.SetBytes(BytesCommMessage)
    _qsnd.Enqueue(cm)
  End Sub
 
#End Region
 
#Region "Private functions"
  Private Sub Sendcm(ByRef _b() As Byte)
    Try
      _sck.BeginSend(_b, 0, _b.Length, SocketFlags.None, AddressOf CallBackSend, _sck)
    Catch
      RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
    End Try
  End Sub
  Private Sub Sending(ByVal Flag As Boolean)
    _sending = Flag
    TimerSendTimeOut.Enabled = Flag
  End Sub
#End Region
 
#Region "Socket delegate CallBack"
 
  'en mode serveur, renvoit un socket connecté à un client
  'puis repasse en attente
  Private Sub CallBackAccept(ByVal async As IAsyncResult)
    Try
      RaiseEvent ConnectionRequestAccepted(_sck.EndAccept(async))
      _sck.BeginAccept(AddressOf CallBackAccept, _sck)
    Catch
      RaiseEvent ProblemDetected(ErrorType.failed_to_listen)
    End Try
  End Sub
 
  'en mode client, établit la connexion
  Private Sub CallBackConnect(ByVal async As IAsyncResult)
    If Not TimerConnectionTimeOut Is Nothing Then TimerConnectionTimeOut.Enabled = False
    Try
      _sck.EndConnect(async)
      RaiseEvent Connected()
      TimerSend.Enabled = True
      _bytes = New Byte(_sck.ReceiveBufferSize) {}
      _sck.BeginReceive(_bytes, 0, _sck.ReceiveBufferSize, SocketFlags.None, AddressOf CallBackReceive, _sck)
    Catch
      RaiseEvent ProblemDetected(ErrorType.connection_failed)
    End Try
  End Sub
 
  'réception de données, puis se remet en attente
  Private Sub CallBackReceive(ByVal async As IAsyncResult)
    Dim size As Integer
    Try
      size = _sck.EndReceive(async)
      If size > 0 Then
        Dim cm As New CommMessage
        cm.SetBytes(_bytes)
        If cm.Order = "" AndAlso cm.Message = "" Then
          If cm.idCode = _last_send.idCode Then Sending(False)
        Else
          If _last_rcv.idCode <> cm.idCode Then _qrcv.Enqueue(cm)
          _last_rcv = cm
          Sendcm(cm.ConfirmSequence)
        End If
      Else
        RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
      End If
      _bytes = New Byte(_sck.ReceiveBufferSize) {}
      _sck.BeginReceive(_bytes, 0, _sck.ReceiveBufferSize, SocketFlags.None, AddressOf CallBackReceive, _sck)
    Catch
      RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
    End Try
  End Sub
 
  'envoi des données terminées
  Private Sub CallBackSend(ByVal async As IAsyncResult)
    Try
      _sck.EndSend(async)
    Catch
      RaiseEvent ProblemDetected(ErrorType.seems_disconnected)
    End Try
  End Sub
 
#End Region
 
End Class