static public Ipv4Header Create(byte[] ipv4Packet, ref int bytesCopied)
{
Ipv4Header ipv4Header = new Ipv4Header();
// Make sure byte array is large enough to contain an IPv4 header
if (ipv4Packet.Length < Ipv4Header.Ipv4HeaderLength)
{
return(null);
}
// Decode the data in the array back into the class properties
ipv4Header.ipVersion = (byte)((ipv4Packet[0] >> 4) & 0xF);
ipv4Header.ipLength = (byte)(ipv4Packet[0] & 0xF);
ipv4Header.ipTypeOfService = ipv4Packet[1];
ipv4Header.ipTotalLength = BitConverter.ToUInt16(ipv4Packet, 2);
ipv4Header.ipId = BitConverter.ToUInt16(ipv4Packet, 4);
ipv4Header.ipOffset = BitConverter.ToUInt16(ipv4Packet, 6);
ipv4Header.ipTtl = ipv4Packet[8];
ipv4Header.ipProtocol = ipv4Packet[9];
ipv4Header.ipChecksum = BitConverter.ToUInt16(ipv4Packet, 10);
ipv4Header.ipSourceAddress = new IPAddress(BitConverter.ToUInt32(ipv4Packet, 12));
ipv4Header.ipDestinationAddress = new IPAddress(BitConverter.ToUInt32(ipv4Packet, 16));
bytesCopied = ipv4Header.Length;
return(ipv4Header);
}
public UdpHeader() : base()
{
srcPort = 0;
destPort = 0;
udpLength = 0;
udpChecksum = 0;
ipv4PacketHeader = null;
}
private static Ipv4Header BuildIPV4Header(IPAddress sourceAddress, IPAddress destAddress, int
messageSize)
{
Ipv4Header ipv4Packet = new Ipv4Header();
// Build the IPv4 header
Console.WriteLine("Building the IPv4 header...");
ipv4Packet.Version = 4;
ipv4Packet.Protocol = (byte)ProtocolType.Udp;
ipv4Packet.Ttl = 2;
ipv4Packet.Offset = 0;
ipv4Packet.Length = (byte)Ipv4Header.Ipv4HeaderLength;
ipv4Packet.TotalLength = (ushort)System.Convert.ToUInt16(Ipv4Header.Ipv4HeaderLength + UdpHeader.UdpHeaderLength + messageSize);
ipv4Packet.SourceAddress = sourceAddress;
ipv4Packet.DestinationAddress = destAddress;
return(ipv4Packet);
}
/// <summary>
/// To do checksum, need to define headers
/// </summary>
private static void SendUDPPacket()
{
Console.WriteLine("Building the packet header...");
byte[] builtPacket, payLoad;
ArrayList headerList = new ArrayList();
Socket rawSocket = null;
SocketOptionLevel socketLevel = SocketOptionLevel.IP;
IPAddress bindAddress = IPAddress.Any;
IPAddress sourceAddress = IPAddress.Parse("127.0.0.1");
IPAddress destAddress = IPAddress.Parse("127.0.0.1");
ushort sourcePort = 5150;
ushort destPort = 1234;
while (true)
{
headerList.Clear();
Console.WriteLine("\nPlease enter a message to send to server and hit enter");
var message = Console.ReadLine();
Console.WriteLine("You enter - " + message);
if (string.IsNullOrWhiteSpace(message))
{
Console.WriteLine("OK, Try again.");
continue;
}
Console.WriteLine("Initialize the payload...");
payLoad = Encoding.ASCII.GetBytes(message);
// Fill out the UDP header first
UdpHeader udpPacket = BuildUDPHeader(payLoad, sourcePort, destPort);
Ipv4Header ipv4Packet = BuildIPV4Header(sourceAddress, destAddress, payLoad.Length);
Console.WriteLine("Setting the IPv4 header for pseudo header checksum...");
udpPacket.ipv4PacketHeader = ipv4Packet;
Console.WriteLine("Adding the IPv4 header to the list of header, encapsulating packet...");
headerList.Add(ipv4Packet);
Console.WriteLine("Adding the UDP header to the list of header, after IP header...");
headerList.Add(udpPacket);
Console.WriteLine("Converting the header classes into the binary...");
builtPacket = udpPacket.BuildPacket(headerList, payLoad);
Console.WriteLine("Message Length ={0}, Total Packet Length = {1}", payLoad.Length, builtPacket.Length);
Console.WriteLine("Creating the raw socket using Socket()...");
rawSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
Console.WriteLine("Binding the socket to the specified interface using Bind()...");
rawSocket.Bind(new IPEndPoint(bindAddress, 0));
Console.WriteLine("Setting the HeaderIncluded option for IP header...");
try
{
// Send the packet!
Console.WriteLine("Sending the packet...");
int rc = rawSocket.SendTo(builtPacket, new IPEndPoint(destAddress, destPort));
Console.WriteLine("send {0} bytes to {1}", rc, destAddress);
byte[] echoedDataFromServer = new byte[builtPacket.Length];
rawSocket.Receive(echoedDataFromServer);
Console.WriteLine("Data Received from Server {0} bytes to {1}", rc, destAddress);
Console.WriteLine("Sent packet's checksum = {0}", udpPacket.Checksum);
// offset for checksum will be 26 and checksum size is 2 bytes
byte[] checksumArray = new byte[2];
Array.Copy(echoedDataFromServer, 26, checksumArray, 0, 2);
var checksumOfReceivedPacket =
(ushort)IPAddress.NetworkToHostOrder((short)BitConverter.ToUInt16(checksumArray, 0));
Console.WriteLine("Received packet's checksum = {0}", checksumOfReceivedPacket);
Console.WriteLine(udpPacket.Checksum != checksumOfReceivedPacket
? "Checksum of sent packet and received packet don't match."
: "Checksum of sent packet and received packet match.");
}
catch (SocketException err)
{
Console.WriteLine("Socket error occurred: {0}", err.Message);
}
finally
{
// Close the socket
Console.WriteLine("Closing the socket...");
rawSocket.Close();
}
}
}