How to send raw data over a network?

Question

Hi everyone!

I've same data stored in a byte-array. The data contains a IPv4 packet (which contains a udp-packet).

I want to send these array raw over the network using C# (preferred) or C++. I don't want to use C#'s udp-client for example.

Does anyone know how to perform this?

Sorry for my bad English and thanks for your help in advance!!!

Answer 1

Try raw sockets (specify SOCK_RAW for the socket type).
You will be responsible for calculating the IP checksums as well. This can be a little annoying.

Answer 2

using System.Net;
using System.Net.Sockets;

public class Test
{
    public void Send(byte[] rawData, IPEndPoint target)
    {
        // change what you pass to this constructor to your needs
        Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IPv4);

        try
        {
            s.Connect(target);
            s.Send(rawData);
        }
        catch(Exception ex)
        {
            // handle this exception
        }
    }
}

Answer 3

When you have raw data (ie a byte-array) and you want to send it over a network, then you need some sort of encoding:

1. If you send multiple blocks (whole arrays), the recipient needs to be able to differentiate between the end of one and the start of the next.
2. If the data is really large its is better to split it into smaller blocks (yes, packets) to play well with other users of the network.
3. You need to know that the data is error-free at the client as networks have the tendency to be unreliable at exactly the wrong time for you.

Encoding solves the first point above.
TCP is the conventional solution to the second two points.

Examples of encoding are:

• HTTP encodes the length in cr delimited lines, then a pure binary blob.
• Text Files could be ctrl-z delimited.
• XML can be delimited simply by its syntax of tags.

Answer 4

I found a solution for may problem: see answer at: http://stackoverflow.com/questions/2493384/how-to-fake-source-ip-address-of-a-udp-packet

Answer 5

Here is a way to send raw data over NIC http://www.codeproject.com/KB/IP/sendrawpacket.aspx As mentioned above Windows is restricting raw socket operations, you have to modify NDIS driver to be able to send whatever you want. Of course you will then have a problem with digital driver signing on Vista/7 (can be temporary bypassed with test mode).