Python Cookbook

Examining the Microsoft Windows Registry for a List of Name Server Addresses

Credit: Wolfgang Strobl

Problem

You need to find out which DNS name servers are being used, but you’re on Microsoft Windows, so you can’t just parse the resolv.conf file, as you might do on Unix and Unix-like platforms.

Solution

On Windows, DNS servers (like much other information) can be found in the registry, which can be accessed with the standard module _winreg:

import string import _winreg def binipdisplay(s): "convert a binary array of ip addresses to a python list" if len(s)%4!= 0: raise EnvironmentError # well ... ol=[] for i in range(len(s)/4): s1=s[:4] s=s[4:] ip=[] for j in s1: ip.append(str(ord(j))) ol.append(string.join(ip,'.')) return ol def stringdisplay(s): 'convert "d.d.d.d,d.d.d.d" to ["d.d.d.d","d.d.d.d"]' return string.split(s,",") def RegistryResolve( ): """ Return the list of dotted-quads addresses of name servers found in the registry -- tested on NT4 Server SP6a, Win/2000 Pro SP2, XP, ME (each of which has a different registry layout for nameservers!) """ nameservers=[] x=_winreg.ConnectRegistry(None,_winreg.HKEY_LOCAL_MACHINE) try: y= _winreg.OpenKey(x, r"SYSTEM\CurrentControlSet\Services\Tcpip\Parameters") except EnvironmentError: # so it isn't NT/2000/XP # Windows ME, perhaps? try: # for Windows ME y = _winreg.OpenKey(x, r"SYSTEM\CurrentControlSet\Services\VxD\MSTCP") nameserver, dummytype = _winreg.QueryValueEx(y,'NameServer') if nameserver and not (nameserver in nameservers): nameservers.extend(stringdisplay(nameserver)) ...