Simple Network Sniffer - Open Source - C# (C-sharp)

// Author: Toomas Kaljus
// http://www.digigrupp.com

namespace DG
{
    public class Application
    {
        public static int Main(string[] args)
        {
            try {
                MainForm AppForm = new MainForm();
                if (args.Length != 0) AppForm.SelectIP.Text = args[0];
                System.Windows.Forms.Application.Run(AppForm);
            } catch {
                return 1;
            }
            return 0;
        }
    }

    public class MainForm : System.Windows.Forms.Form
    {
        System.Windows.Forms.Label SelectIPLabel = new System.Windows.Forms.Label();
        public System.Windows.Forms.ComboBox SelectIP = new System.Windows.Forms.ComboBox();
        System.Windows.Forms.Button StartButton = new System.Windows.Forms.Button(), StopButton = new System.Windows.Forms.Button();
        System.Windows.Forms.CheckBox DnsResolve = new System.Windows.Forms.CheckBox();
        System.Windows.Forms.CheckBox LooseQueue = new System.Windows.Forms.CheckBox();
        System.Windows.Forms.Button SaveButton = new System.Windows.Forms.Button(), ResetButton = new System.Windows.Forms.Button();
        System.Windows.Forms.ListBox ResultBox = new System.Windows.Forms.ListBox();
        System.Threading.Thread Sniffer;
        System.Net.Sockets.Socket Socket;
        const int PacketBufferSize = 65536;
        byte[] PacketBuffer = new byte[PacketBufferSize];
        System.Collections.Specialized.NameValueCollection DNSCache = new System.Collections.Specialized.NameValueCollection();
        
        internal MainForm() : base()
        {
            Text = "Sniffer";
            Width = 400;
            Controls.Add(SelectIPLabel);
            SelectIPLabel.Top = 4;
            SelectIPLabel.Left = 4;
            SelectIPLabel.Text = "Select IP address:";
            Controls.Add(SelectIP);
            SelectIP.Top = 4;
            SelectIP.Left = 104;

    #if NET20
            System.Net.IPAddress[] IPAddress = System.Net.Dns.GetHostAddresses(System.Net.Dns.GetHostName());
            if(IPAddress.Length > 0)
                for (int i=0; i<IPAddress.Length; i++)
                    SelectIP.Items.Add(IPAddress[i].ToString());
    #else
            System.Net.IPHostEntry HostEntry = System.Net.Dns.Resolve(System.Net.Dns.GetHostName());
            if(HostEntry.AddressList.Length > 0)
                for (int i=0; i<HostEntry.AddressList.Length; i++)
                    SelectIP.Items.Add(HostEntry.AddressList[i].ToString());
    #endif

            Controls.Add(StartButton);
            StartButton.Top = 4;
            StartButton.Left = 230;
            StartButton.Text = "Start";
            StartButton.Click += new System.EventHandler(StartButton_Click);
            Controls.Add(StopButton);
            StopButton.Top = 4;
            StopButton.Left = 310;
            StopButton.Text = "Stop";
            StopButton.Click += new System.EventHandler(StopButton_Click);
            StopButton.Enabled = false;
            Controls.Add(DnsResolve);
            DnsResolve.Top = 28;
            DnsResolve.Left = 4;
            DnsResolve.Width = 130;
            DnsResolve.Text = "Resolve Host Names";
            Controls.Add(LooseQueue);
            LooseQueue.Top = 28;
            LooseQueue.Left = 134;
            LooseQueue.Width = 96;
            LooseQueue.Text = "Loose Queue";
            Controls.Add(SaveButton);
            SaveButton.Top = 28;
            SaveButton.Left = 230;
            SaveButton.Text = "Save";
            SaveButton.Click += new System.EventHandler(SaveButton_Click);
            Controls.Add(ResetButton);
            ResetButton.Top = 28;
            ResetButton.Left = 310;
            ResetButton.Text = "Reset";
            ResetButton.Click += new System.EventHandler(ResetButton_Click);
            Controls.Add(ResultBox);
            ResultBox.Top = 54;
            ResultBox.Left = 4;
            ResultBox.Width = 384;
            ResultBox.Height = 224;
            ResultBox.Anchor = (System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Left | System.Windows.Forms.AnchorStyles.Right | System.Windows.Forms.AnchorStyles.Top);
        }

        private void StartButton_Click(object Sender, System.EventArgs e)
        {
            if (SelectIP.Text == "") {
                System.Windows.Forms.MessageBox.Show("Please select IP!");
                return;
            }
            StartButton.Enabled = false;
            Sniffer = new System.Threading.Thread(new System.Threading.ThreadStart(RunReceiver));
            Sniffer.Start();
        }

        private void StopButton_Click(object Sender, System.EventArgs e)
        {
            StopButton.Enabled = false;
        }

        private void SaveButton_Click(object Sender, System.EventArgs e)
        {
            using (System.IO.StreamWriter sw = new System.IO.StreamWriter(System.IO.Path.GetDirectoryName(System.Windows.Forms.Application.ExecutablePath) + "\\iplog.txt")) {
                for (int i=0; i<ResultBox.Items.Count; i++) sw.WriteLine(System.DateTime.Now + " " + ResultBox.Items[i].ToString());
            }
        }

        private void ResetButton_Click(object Sender, System.EventArgs e)
        {
            ResultBox.Items.Clear();
        }

        protected override void Dispose(bool disposing)
        {
            if (StopButton.Enabled) StopButton_Click(null, null);
            while (StopButton.Enabled) System.Threading.Thread.Sleep(1);
            base.Dispose(disposing);
        }

        private void RunReceiver()
        {
            StopButton.Enabled = true;
            try {
                try {
                    Socket = new System.Net.Sockets.Socket(System.Net.Sockets.AddressFamily.InterNetwork, System.Net.Sockets.SocketType.Raw, System.Net.Sockets.ProtocolType.IP);
                    try {
                        Socket.Bind(new System.Net.IPEndPoint(System.Net.IPAddress.Parse(SelectIP.Text), 0));
                        Socket.SetSocketOption(System.Net.Sockets.SocketOptionLevel.IP, System.Net.Sockets.SocketOptionName.HeaderIncluded, 1);
                        Socket.IOControl(unchecked((int)0x98000001), new byte[4]{1, 0, 0, 0}, new byte[4]);
                        while (StopButton.Enabled) {
                            System.IAsyncResult ar = Socket.BeginReceive(PacketBuffer, 0, PacketBufferSize, System.Net.Sockets.SocketFlags.None, new System.AsyncCallback(CallReceive), this);
                            while (Socket.Available == 0) {
                                System.Threading.Thread.Sleep(1);
                                if (!StopButton.Enabled) break;
                            }
                            if (!StopButton.Enabled) break;
                            int Size = Socket.EndReceive(ar);
                            if (!LooseQueue.Checked) ExtractBuffer();
                        }
                    } finally {
                        if (Socket != null) {
                            Socket.Shutdown(System.Net.Sockets.SocketShutdown.Both);
                            Socket.Close();
                        }
                    }
                } finally {
                    StopButton.Enabled = false;
                    StartButton.Enabled = true;
                }
            } catch (System.Threading.ThreadAbortException) {
            } catch (System.Exception E) {
                System.Windows.Forms.MessageBox.Show(E.ToString());
            }
            StartButton.Enabled = true;
        }

        public virtual void CallReceive(System.IAsyncResult ar)
        {
            if (LooseQueue.Checked) ExtractBuffer();
        }

        protected void ExtractBuffer()
        {
            IPPacket IP = new IPPacket(ref PacketBuffer);

            string SourceAddress = IP.SourceAddress.ToString();
            string DestinationAddress = IP.DestinationAddress.ToString();

            if (DnsResolve.Checked) {
                string HostName = DNSCache[SourceAddress];
                if (HostName == null) {
                    DNSCache[SourceAddress] = "";
    #if NET20
    try {
                    HostName = System.Net.Dns.GetHostEntry(SourceAddress).HostName;
    } catch {
                    HostName = "";
    }
    #else
                    HostName = System.Net.Dns.Resolve(SourceAddress).HostName;
    #endif
                    DNSCache[SourceAddress] = HostName;
                }
                if (HostName != SourceAddress) SourceAddress += " " + HostName;
                HostName = DNSCache[DestinationAddress];
                if (HostName == null) {
                    DNSCache[DestinationAddress] = "";
    #if NET20
    try {
                    HostName = System.Net.Dns.GetHostEntry(SourceAddress).HostName;
    } catch {
                    HostName = "";
    }
    #else
                    HostName = System.Net.Dns.Resolve(SourceAddress).HostName;
    #endif
                    DNSCache[DestinationAddress] = HostName;
                }
                if (HostName != DestinationAddress) DestinationAddress += " " + HostName;
            }

            if (IP.TCP != null) {
                string Data = System.Text.RegularExpressions.Regex.Replace(System.Text.Encoding.ASCII.GetString(IP.TCP.PacketData), @"[^a-zA-Z_0-9\.\@\- ]", "");

                ResultBox.Items.Insert(0, "TCP " + SourceAddress + ":" + IP.TCP.SourcePort + " --> " + DestinationAddress + ":" + IP.TCP.DestinationPort + " " + Data);

            } else
            if (IP.UDP != null) {
                string Data = System.Text.RegularExpressions.Regex.Replace(System.Text.Encoding.ASCII.GetString(IP.UDP.PacketData), @"[^a-zA-Z_0-9\.\@\- ]", "");

                ResultBox.Items.Insert(0, "UDP " + SourceAddress + ":" + IP.UDP.SourcePort + " --> " + DestinationAddress + ":" + IP.UDP.DestinationPort + " " + Data);

            } else
            if (IP.ICMP != null) {
                string Data = System.Text.RegularExpressions.Regex.Replace(System.Text.Encoding.ASCII.GetString(IP.ICMP.PacketData), @"[^a-zA-Z_0-9\.\@\- ]", "");

                ResultBox.Items.Insert(0, "ICMP " + SourceAddress + " --> " + DestinationAddress + " " + IP.ICMP.Message + " " + Data);

            } else
            ResultBox.Items.Insert(0, IP.Protocol + " " + SourceAddress + " --> " + DestinationAddress);
        }
    }
}