Imports System.Net
Imports System.IO

Module Module1

    Dim Sock As New Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)
    Dim Port As String = 81
    Dim Ip As String = "83.135.207.179"
    Dim Buffer(&H7FFF + 6 - 1) As Byte


    Sub Main()
        Sock.BeginConnect(IPAddress.Parse(Ip), Port, New AsyncCallback(AddressOf ConnectEnd), Nothing)
        Console.ReadKey()
    End Sub

    Sub ConnectEnd(ByVal ar As IAsyncResult)
        Try
            sock.EndConnect(ar)
            sock.BeginReceive(buffer, 0, buffer.Length, Sockets.SocketFlags.None, New AsyncCallback(AddressOf EndReceive), 0)
        Catch ex As Exception
            Console.WriteLine(ex.ToString)
        End Try
    End Sub
    Sub EndReceive(ByVal ar As IAsyncResult)

        Dim ReceivedBytes As Int32
        Dim Offset As Int32

        Offset = ar.AsyncState

        Try
            ReceivedBytes = Sock.EndReceive(ar)
        Catch ex As Exception
            Console.WriteLine(ex.ToString)
        End Try

        '#### check if connection is lost ####
        If ReceivedBytes = 0 Then
            Console.WriteLine("connection lost")
            Exit Sub
        End If

        '#### split data into silkroad packets               ####
        '#### write remaing bytes at beginning of the buffer ####
        '#### set new offset                                 ####
        CreatPackets(Buffer, ReceivedBytes, Offset)
        'Console.WriteLine(BitConverter.ToString(Buffer, 0, ReceivedBytes))
        '#### begin next receive ####
        Sock.BeginReceive(Buffer, 0 + Offset, Buffer.Length - Offset, Sockets.SocketFlags.None, New AsyncCallback(AddressOf EndReceive), Offset)

    End Sub


    Sub CreatPackets(ByRef buffer() As Byte, ByRef ReceivedBytes As Int32, ByRef Offset As Int32)

        Dim br As New BinaryReader(New MemoryStream(buffer))
        Dim BytesInBuffer As Int32 = ReceivedBytes + Offset

        Dim packetlen As Int16
        Dim packetOPC As Int16
        Dim packetSecBytes As Int16
        Dim packetdata() As Byte

        Do
            '#### check if header is complett ####
            If br.BaseStream.Position + 6 <= BytesInBuffer Then
                packetlen = br.ReadInt16()
                packetOPC = br.ReadInt16()
                packetSecBytes = br.ReadInt16()
            Else 'header not complett
                Exit Do
            End If

            '#### check if we have all data bytes ####
            If br.BaseStream.Position + packetlen <= BytesInBuffer Then
                packetdata = br.ReadBytes(packetlen)
            Else
                br.BaseStream.Position -= 6 ' header belong to not complett packet --> 6 byte back in stream
                Exit Do
            End If

            '#### packet complett let's print it ####
            Console.WriteLine("len:{0} opc:{1} sec:{2} data:{3}", _
                        packetlen.ToString("X2"), _
                        packetOPC.ToString("X2"), _
                        packetSecBytes.ToString("X2"), _
                        BitConverter.ToString(packetdata))

        Loop

        '#### check if we read all bytes from the buffer ####
        If br.BaseStream.Position = ReceivedBytes + Offset Then
            Offset = 0 'set new offset
        Else 'didn't read all bytes --> calc the offset and write the remaining bytes to the beginning of the buffer
            Dim bw As New BinaryWriter(New MemoryStream(buffer))

            Offset = BytesInBuffer - br.BaseStream.Position 'set new offset
            bw.Write(br.ReadBytes(Offset)) ' write remaining bytes back to beginning of the buffer

            bw.Flush()
            bw.Close()
        End If

        br.Close()

    End Sub


End Module