以下的代码的原作是opensource的一个叫sniffer.net的，用vb.net写的，这里只是简单的用c#翻译了一下，暂时还只能监控所有数据包，不能监控某一个进程的数据包,代码如下：
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Runtime.InteropServices;

namespace UpdateTester
{
 /**//// <summary>
 /// Monitor 的摘要说明。
 /// </summary>
 public class Monitor
 {
  public delegate void NewPacketEventHandler(Monitor m, Packet p);
  public event NewPacketEventHandler NewPacket;
  private Socket m_Monitor;
  private IPAddress m_Ip;
  private byte[] m_Buffer = new byte[65535];
  private const System.Int32 IOC_VENDOR = 0x18000000;
  private const int IOC_IN = -2147483648;
  private const int SIO_RCVALL = IOC_IN ^ IOC_VENDOR ^ 1;
  private const int SECURITY_BUILTIN_DOMAIN_RID = 0x20;
  private const int DOMAIN_ALIAS_RID_ADMINS = 0x220;

  public System.Net.IPAddress IP
  {
   get { return m_Ip; }
  }

  public byte[] Buffer
  {
   get { return m_Buffer; }
  }

  public Monitor()
  {
   //
   // TODO: 在此处添加构造函数逻辑
   //
  }

  public Monitor(IPAddress IpAddress)
  {
   if (!(Environment.OSVersion.Platform == PlatformID.Win32NT) && Environment.OSVersion.Version.Major<5)
   {
    throw new NotSupportedException("This program requires Windows 2000, Windows XP or Windows .NET Server!");
   }
   m_Ip = IpAddress;
  }

  public void Start()
  {
   if (m_Monitor==null)
   {
    try
    {
     m_Monitor = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP);
     m_Monitor.Bind(new IPEndPoint(IP, 0));
     m_Monitor.IOControl(SIO_RCVALL, BitConverter.GetBytes(1), null);
     m_Monitor.BeginReceive(m_Buffer, 0, m_Buffer.Length, SocketFlags.None, new AsyncCallback(OnReceive), null);
    }
    catch (Exception e)
    {
     m_Monitor = null;
     throw new SocketException();
    }
   }
  }

  public void Stop()
  {
   if (m_Monitor!=null)
   {
    m_Monitor.Close();
   }
   m_Monitor = null;
  }

  public void OnReceive(System.IAsyncResult ar)
  {
   try
   {
    int received = m_Monitor.EndReceive(ar);

    try
    {
     if (m_Monitor!=null)
     {
      byte[] pkt = new byte[received];
      Array.Copy(Buffer, 0, pkt, 0, received);
      OnNewPacket(new Packet(pkt, DateTime.Now));
     }
    }
    catch(Exception e)
    {
     throw;
    }

    m_Monitor.BeginReceive(Buffer, 0, Buffer.Length, SocketFlags.None, new AsyncCallback(OnReceive), null);
   }
   catch (Exception e)
   {

   }
  }

  protected void OnNewPacket(Packet p)
  {
   NewPacket(this, p);
  }
 }
}

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

namespace UpdateTester
{