Network Programming problems

Question

Hi
I've taken this code from one of my tutors for my dissertation. The program is SimplePing, its on the net somewhere but I'll post it here anyway:
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
class SimplePing
{
public static void Main(string[] argv)
{
byte[] data = new byte[1024];
int recv;
Socket host = new Socket(AddressFamily.InterNetwork, SocketType.Raw,
ProtocolType.Icmp);
IPEndPoint iep = new IPEndPoint(IPAddress.Parse(argv[0]), 0);
EndPoint ep = (EndPoint)iep;
ICMP packet = new ICMP();
packet.Type = 0x08;
packet.Code = 0x00;
packet.Checksum = 0;
Buffer.BlockCopy(BitConverter.GetBytes((short)1), 0, packet.Message, 0, 2);
Buffer.BlockCopy(BitConverter.GetBytes((short)1), 0, packet.Message, 2, 2);
data = Encoding.ASCII.GetBytes("test packet");
Buffer.BlockCopy(data, 0, packet.Message, 4, data.Length);
packet.MessageSize = data.Length + 4;
int packetsize = packet.MessageSize + 4;
UInt16 chcksum = packet.getChecksum();
packet.Checksum = chcksum;
host.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 3000);
host.SendTo(packet.getBytes(), packetsize, SocketFlags.None, iep);
try
{
data = new byte[1024];
recv = host.ReceiveFrom(data, ref ep);
} catch (SocketException)
{
Console.WriteLine("No response from remote host");
return;
}
ICMP response = new ICMP(data, recv);
Console.WriteLine("response from: {0}", ep.ToString());
Console.WriteLine(" Type {0}", response.Type);
Console.WriteLine(" Code: {0}", response.Code);
int Identifier = BitConverter.ToInt16(response.Message, 0);
int Sequence = BitConverter.ToInt16(response.Message, 2);
Console.WriteLine(" Identifier: {0}", Identifier);
Console.WriteLine(" Sequence: {0}", Sequence);
string stringData = Encoding.ASCII.GetString(response.Message, 4, response.MessageSize - 4);
Console.WriteLine(" data: {0}", stringData);

host.Close();
}
}
 
What I want to do is split the program in half so one of the computers communicating sits and waits until it sees a icmp request packet that is sent from the other computer running the full version of simple ping. This is what I've done so far:
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
class SimplePing
{
public static void Main()
{
byte[] data = new byte[1024];
int recv = 0;
Socket host = new Socket(AddressFamily.InterNetwork, SocketType.Raw,
ProtocolType.Icmp);
IPEndPoint iep = new IPEndPoint(IPAddress.Any, 0);
EndPoint ep = (EndPoint)iep;
host.Bind(ep);

data = new byte[1024];
Console.WriteLine("Waiting to receive datagrams from client...");
recv = host.ReceiveFrom(data, ref ep);
host.Close();


ICMP response = new ICMP(data, recv);
Console.WriteLine("response from: {0}", ep.ToString());
Console.WriteLine(" Type {0}", response.Type);
Console.WriteLine(" Code: {0}", response.Code);
int Identifier = BitConverter.ToInt16(response.Message, 0);
int Sequence = BitConverter.ToInt16(response.Message, 2);
Console.WriteLine(" Identifier: {0}", Identifier);
Console.WriteLine(" Sequence: {0}", Sequence);
string stringData = Encoding.ASCII.GetString(response.Message, 4, response.MessageSize - 4);
Console.WriteLine(" data: {0}", stringData);
host.Close();
}
}
If you want to rebuild this program it might help to download the code for ICMP.cs as follows:
using System;
using System.Net;
using System.Text;
class ICMP
{
public byte Type;
public byte Code;
public UInt16 Checksum;
public int MessageSize;
public byte[] Message = new byte[1024];
public ICMP()
{
}
public ICMP(byte[] data, int size)
{
Type = data[20];
Code = data[21];
Checksum = BitConverter.ToUInt16(data, 22);
MessageSize = size - 24;
Buffer.BlockCopy(data, 24, Message, 0, MessageSize);
}
public byte[] getBytes()
{
byte[] data = new byte[MessageSize + 9];
Buffer.BlockCopy(BitConverter.GetBytes(Type), 0, data, 0, 1);
Buffer.BlockCopy(BitConverter.GetBytes(Code), 0, data, 1, 1);
Buffer.BlockCopy(BitConverter.GetBytes(Checksum), 0, data, 2, 2);
Buffer.BlockCopy(Message, 0, data, 4, MessageSize);
return data;
}
public UInt16 getChecksum()
{
UInt32 chcksm = 0;
byte[] data = getBytes();
int packetsize = MessageSize + 8;
int index = 0;
while ( index < packetsize)
{
chcksm += Convert.ToUInt32(BitConverter.ToUInt16(data, index));
index += 2;
}
chcksm = (chcksm >> 16) + (chcksm & 0xffff);
chcksm += (chcksm >> 16);
return (UInt16)(~chcksm);
}
}
Any suggestions would be helpful, thanks
Dan