Recieved TCP packet drops first byte

[jny0]

Hi,

I've been using some code which I found on the net, and have noticed that the first byte is never recieved. Annoyingly, this contains the MAC addresses, which is the bit I want. Can anyone help? Below is the relevant snippits:

Public Sub [Start]()
If m_Socket Is Nothing Then
Try
m_Socket = New Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP)
m_Socket.Bind(New IPEndPoint(m_IP, 0))
m_Socket.IOControl(SIO_RCVALL, BitConverter.GetBytes(1), Nothing)
m_Socket.BeginReceive(m_Buffer, 0, m_Buffer.Length, SocketFlags.None, New AsyncCallback(AddressOf OnReceive), Nothing)
Catch
m_Socket = Nothing
Throw New SocketException
End Try
End If
End Sub

Private Sub OnReceive(ByVal ar As IAsyncResult)

Try
Dim received As Integer = m_Socket.EndReceive(ar)
Try
If Not m_Socket Is Nothing Then
ReDim m_pkt(received - 1)
Array.Copy(Buffer, 0, m_pkt, 0, received)
OnNewPacket(New Packet(m_pkt))

End If
Catch ex As Exception
'Do Nothing -this is intended
End Try
m_Socket.BeginReceive(Buffer, 0, Buffer.Length, SocketFlags.None, New AsyncCallback(AddressOf OnReceive), Nothing)

Catch
[Stop]()
End Try
End Sub

[Grimfort]

Generally the first missing item is caused when you try to use an array and start at 1 instead of 0
The code above seems to contain 0's are you sure your not dropping it in code somewhere else?

[jny0]

I've looked through, and I don't think so. I've realised I've made a mistake in the last posting though. I'm not loosing the first byte, I'm losing the first 14 bytes, which actually constitute the Ethernet 2 part of the frame. I get everything from Internet Protocol onwards. This pretty much rules out an array index problem, and rules in a code for socket problem.

[Grimfort]

Are you sure that is not done on purpose? The socket is dealing with the sending/receiving part so would remove the 'computer' bits from it to just give you the data itself. I have not used sockets directly as I use a 3rd party control, but would make sense to me that all you get is the data you sent itself.

[Grimfort]

Here ya go, try this: msdn

[jny0]

Many thanks. Ended up using the arp interrogation method.