packet truncation

[datasto...@gmail.com]

Hi everyone,

I'm try to receive data from a network device who communicate via network interface.

This is my code of receiving data:

           using (PacketCommunicator communicator = selectedDevice.Open(   65536,  
                                                                            PacketDeviceOpenAttributes.Promiscuous,
                                                                            1000))
            {
               
                // Check the link layer. We support only Ethernet for simplicity.
                if (communicator.DataLink.Kind != DataLinkKind.Ethernet)
                {
                    MessageBox.Show("This program works only on Ethernet networks.");
                    return;
                }


                string strFilter = "src host 192.168.3.67";
                // Compile the filter
                using (BerkeleyPacketFilter filter = communicator.CreateFilter(strFilter))
                {
                    // Set the filter
                    communicator.SetFilter(filter);
                }
               
                while (true)
                {
                    try
                    {
                        // Read and dispatch packets until EOF is reached
                        communicator.ReceivePackets(0, DispatcherHandler);
                    }
                    catch (Exception ex)
                    {
                        _Parent.Log.LogError(ex.Message);
                        continue;
                    }
               }
            }

This is my callback function:

 

      private void DispatcherHandler(Packet packet)
        {
                // Create two different encodings.
                Encoding ascii = Encoding.ASCII;
                Encoding unicode = Encoding.Unicode;

                //Converto il pacchetto in formato UNICODE
                string unicodeString = Encoding.UTF8.GetString(packet.Buffer, 0, packet.Length);
                // Convert the string into a byte array.
                byte[] unicodeBytes = unicode.GetBytes(unicodeString);
                // Perform the conversion from one encoding to the other.
                byte[] asciiBytes = Encoding.Convert(unicode, ascii, unicodeBytes);
                // Convert the new byte[] into a char[] and then into a string.
                char[] asciiChars = new char[ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)];
                ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0);
                string asciiString = new string(asciiChars);

[...]

//asciiString is truncate!!

Normally (if I get from the device short ansewer) the program works but when the device send long packet I have a truncation (1514 car truncation int the packet).

Wireshark instead retrive full packets.

I search in the documentation, in the Q&A and I don't find similar problem. 

Also I've try to:

-increase the snapshotlenght in the Open comunicator call

-increase the read timeout in the Open comunicator call

-change the communicator.SetKernelBufferSize.

Any ideas?

[datasto...@gmail.com]

Ok, I've resolved.

The problem is the fragmentation of the packet.

I've do a reassembly of sequential packet only in case of fragmentation.