这几天做ASP.Net追捕，也算是我入门吧。思路很简单，主要就是识别远程主机传回的Banner，
判断远程主机服务器。这可能不够准确，因为合格的管理员可能会去修改Banner。

代码如下（从我的Web追捕里找出来的，用VB.Net）

Dim swWriter As StreamWriter
   '用以向网络基础数据流传送数据
   Dim nsStream As NetworkStream
   '创建发送数据的网络基础数据流
   Dim tcpClient2 As TcpClient
   '通过它实现向远程主机提出TCP连接申请
   Dim sHostName As String
   Dim srRead As StreamReader
   '从网络基础数据流中读取数据
   'HTTP服务追捕
   If TcpConnect(ZSIP, 80) = "CG" Then
OppHTTP.Text = "HTTP服务已开启！服务软件类型：未知"
Try
  'tcpClient = New TcpClient(IPAddress, Port)
  tcpClient2 = New TcpClient(ZSIP.ToString(), 80)
  tcpClient2.ReceiveTimeout = 1000000
  tcpClient2.SendTimeout = 1000000
  '对远程主机的8000端口提出TCP连接申请
  nsStream = tcpClient2.GetStream()
  '通过申请，并获取传送数据的网络基础数据流
  swWriter = New StreamWriter(nsStream)
  swWriter.WriteLine("Get /index.htm HTTP/1.1")
  swWriter.WriteLine("Host:" & IP.Text)
  swWriter.WriteLine("Accept:*/*")
  swWriter.WriteLine("Referer:")
  swWriter.WriteLine()
  '刷新当前数据流中的数据
  swWriter.Flush()
  srRead = New StreamReader(nsStream, Encoding.Default)
  '以得到的网络基础数据流来初始化StreamReader实例
  Dim L As Integer = 0
  Do While Not srRead.Peek = -1 And L < 20
   StrHttp = StrHttp & srRead.ReadLine()
   L = L + 1
  Loop
  If InStr(StrHttp, "IIS") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：IIS 版本未知"
   SystemFW = "WindowsNT/2000/XP/2003"
  End If
  If InStr(StrHttp, "Apache") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 版本未知"
  End If
  If InStr(StrHttp, "Netscape-Enterprise") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Netscape-Enterprise 版本未知"
  End If
  If InStr(StrHttp, "Microsoft-IIS/5.0") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：IIS 5.0"
   SystemFW = "Windows2000"
  End If
  If InStr(StrHttp, "Microsoft-IIS/5.1") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：IIS 5.1"
   SystemFW = "Windows2000/XP"
  End If
  If InStr(StrHttp, "Microsoft-IIS/6.0") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：IIS 6.0"
   SystemFW = "Windows2003"
  End If
  If InStr(StrHttp, "Apache/2") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 2.x"
  End If
  If InStr(StrHttp, "Apache/2.0.54") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 2.0.54"
  End If
  If InStr(StrHttp, "Apache/2.0.52") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 2.0.52"
  End If
  If InStr(StrHttp, "Apache/2.1.6") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 2.1.6"
  End If
  If InStr(StrHttp, "Apache/1.3.2") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 1.3.x"
  End If
  If InStr(StrHttp, "Apache/1.3.20") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 1.3.20"
  End If
  If InStr(StrHttp, "Apache/1.3.23") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 1.3.23"
  End If
  If InStr(StrHttp, "Apache/1.3.26") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 1.3.26"
  End If
  If InStr(StrHttp, "Apache/1.3.27") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 1.3.27"
  End If
  If InStr(StrHttp, "Apache/1.3.33") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Apache 1.3.33"
  End If
  If InStr(StrHttp, "Netscape-Enterprise/4.1") > 0 Then
   OppHTTP.Text = "HTTP服务已开启！服务软件类型：Netscape-Enterprise 4.1"
  End If
  If InStr(StrHttp, "Unix") > 0 Then
   SystemFW = "类Unix/Linux系统"
  End If
Catch
End Try

因为是摘出来的，所以有的变量没有定义，大家自己去琢磨吧。