Hey, Scripting Guy! At work we need to use a proxy server to connect to the Internet; when I take my laptop home to work, however, I don’t need to use a proxy server. I know I can use the Internet Options in Control Panel to change between using a proxy server and not using a proxy server; is there any way to switch between the two using a script?

— EA

Hey, EA. Let’s hope there’s a way to do this using a script; if there isn’t, this column will be much shorter than usual. (Of course, many people might argue that that wouldn’t be such a bad thing.) If you aren’t sure what EA is talking about, he’s talking about the bottom set of options (the options in the section labeled Proxy server) in the following dialog box:

This, by the way, is a fairly common scenario: lots of companies use proxy servers on their internal network, but few Internet Service Providers use proxy servers for their consumer networks. If you use a laptop computer both at home and at work, you’ll constantly find yourself switching between using a proxy server and not using a proxy server.

So how can we do this using a script? Well, as it turns out there are three registry values that control these settings. (Yes, from the dialog box it appears as though there are four settings that need to be controlled. Don’t worry; we’ll explain how this all works.) These three registry values – found in the HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings key in the registry – include:

Got all that? Now that we know the registry values that need to be configured (as well as how to configure them) the rest is as easy as writing a WMI script that enables the proxy server, specifies the proxy server address and port, and tells Internet Explorer to bypass the proxy server for local addresses:

Const HKEY_CURRENT_USER = &H80000001

strComputer = “.”
Set objRegistry = GetObject(“winmgmts:\\” & strComputer & “\root\default:StdRegProv”)
strKeyPath = “SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings”
strValueName = “ProxyEnable”
dwValue = 1
objRegistry.SetDWORDValue HKEY_CURRENT_USER, strKeyPath, strValueName, dwValue
strValueName = “ProxyServer”
strValue = “svcproxy:80”
objRegistry.SetStringValue HKEY_CURRENT_USER, strKeyPath, strValueName, strValue
strValueName = “ProxyOverride”
strValue = “<local>”
objRegistry.SetStringValue HKEY_CURRENT_USER, strKeyPath, strValueName, strValue

The script starts off by defining a constant named HKEY_CURRENT_USER and setting the value to &H80000001; we’ll use this constant later on to tell the script we want to work with the HKCU portion of the registry. We then connect to the WMI service, this time binding to the root\default namespace and the StdRegProv class (the WMI class used for reading and writing registry values).

After we make the connection we next assign the registry path (SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings) to a variable named strKeyPath; we then assign the registry value (ProxyEnable) and the configuration value (1) to the variables strValueName and dwValue. We now have all the information we need to call the SetDWORDValue method and change the value of ProxyEnable to 1:

objRegistry.SetDWORDValue HKEY_CURRENT_USER, strKeyPath, strValueName, dwValue

After that we repeat the same process for ProxyServer and ProxyOverride. Note, however, that both of these registry values have a REG_SZ data type; therefore we use the SetStringValue method instead of SetDWORDValue. (If you have no idea what we’re talking about when we say things like SetDWORDValue and SetStringValue then take a look at the Registry chapter in the Microsoft Windows 2000 Scripting Guide.)

As we noted earlier, disabling the proxy server is much easier: all we have to do is set the value of ProxyEnable to 0:

Const HKEY_CURRENT_USER = &H80000001

strComputer = “.”
Set objRegistry = GetObject(“winmgmts:\\” & strComputer & “\root\default:StdRegProv”)
strKeyPath = “SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings”
strValueName = “ProxyEnable”
dwValue = 0
objRegistry.SetDWORDValue HKEY_CURRENT_USER, strKeyPath, strValueName, dwValue

In fact, after your proxy settings have all been configured (that is, after you’ve initially assigned values to ProxyServer and ProxyOverride), you can toggle back and forth between using a proxy server and not using a proxy server simply by configuring the ProxyEnable key. In other words, after you have a proxy address and port and after you’ve decided what you want to do with the ProxyOverride value then all you need to do is run this script to re-enable use of the proxy server:

Const HKEY_CURRENT_USER = &H80000001

strComputer = “.”
Set objRegistry = GetObject(“winmgmts:\\” & strComputer & “\root\default:StdRegProv”)
strKeyPath = “SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings”
strValueName = “ProxyEnable”
dwValue = 1
objRegistry.SetDWORDValue HKEY_CURRENT_USER, strKeyPath, strValueName, dwValue

To disable the proxy server just set the value of ProxyEnable to 0. It’s that easy.