public static UdpHeader Create(byte[] udpData, ref int bytesCopied)
{
UdpHeader udpPacketHeader = new UdpHeader();
udpPacketHeader.srcPort = BitConverter.ToUInt16(udpData, 0);
udpPacketHeader.destPort = BitConverter.ToUInt16(udpData, 2);
udpPacketHeader.udpLength = BitConverter.ToUInt16(udpData, 4);
udpPacketHeader.udpChecksum = BitConverter.ToUInt16(udpData, 6);
return(udpPacketHeader);
}
private static UdpHeader BuildUDPHeader(byte[] payLoad, ushort sourcePort, ushort destPort)
{
Console.WriteLine("Filling out the UDP header...");
UdpHeader udpPacket = new UdpHeader();
udpPacket.SourcePort = sourcePort;
udpPacket.DestinationPort = destPort;
udpPacket.Length = (ushort)(UdpHeader.UdpHeaderLength + payLoad.Length);
udpPacket.Checksum = 0;
return(udpPacket);
}
/// <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();
}
}
}
