Ran into a question from a client the other day that asked how to deal with Internet Connection settings for running HTTP requests. In this case this is an old FoxPro app and it's using WinInet to handle the actual HTTP connection. Another client asked a similar question about using the IE Web Browser control and configuring connection properties. Regardless of platform or tools used to do HTTP connections, you can probably configure custom connection and proxy settings in your application to configure http connection settings manually. However, this is a repetitive process for each application requires you to track system information in your application which is undesirable. Often it's much easier to rely on the system wide proxy settings that Windows provides via the Internet Settings
dialog. The
dialog is a Control Panel applet (inetcpl.cpl) and is the same
dialog that you see when you pop up Internet Explorer's Options dialog: This
dialog controls the Windows connection properties that determine how the Windows HTTP stack connects to the Internet and how Proxy's are used if configured. Depending on how the HTTP client is configured - it can typically inherit and use these global settings. Loading the Settings
Dialog Programmatically The settings
dialog is a Control Panel applet with the name of: inetcpl.cpl and you can use any Shell execution mechanism (Run
dialog, ShellExecute API, Process.Start() in .NET etc.) to invoke the
dialog. Changes made there are immediately reflected in any applications that use the default connection settings. In .NET you can simply do this to bring up the Internet Settings
dialog with the Connection tab enabled: Process.Start("inetcpl.cpl",",4");
In FoxPro you can simply use the
RUN command to execute inetcpl.cpl:
lcCmd = "inetcpl.cpl ,4"
RUN &lcCmd
Using the Default Connection/Proxy Settings
When using WinInet you specify the Http connect type in the call to InternetOpen() like this (FoxPro code here):
hInetConnection=;
InternetOpen(THIS.cUserAgent,0,;
THIS.chttpproxyname,THIS.chttpproxybypass,0)
The second parameter of 0 specifies that the default system proxy settings should be used and it uses the settings from the Internet Settings Connections tab. Other connection options for HTTP connections include 1 - direct (no proxies and ignore system settings), 3 - explicit Proxy specification. In most situations a connection mode setting of 0 should work.
In .NET HTTP connections by default are direct connections and so you need to explicitly specify a default proxy or proxy configuration to use. The easiest way to do this is on the application level in the config file:
<configuration>
<system.net>
<defaultProxy>
<proxy bypassonlocal="False" autoDetect="True" usesystemdefault="True" />
</defaultProxy>
</system.net>
</configuration>
You can do the same sort of thing in code specifying the proxy explicitly and using System.Net.WebProxy.GetDefaultProxy(). So when making HTTP calls to Web Services or using the HttpWebRequest class you can set the proxy with:
StoreService.Proxy = WebProxy.GetDefaultProxy();
All of this is pretty easy to deal with and in my opinion is a way better choice to managing connection settings than having to track this stuff in your own application. Plus if you use default settings, most of the time it's highly likely that the connection settings are already properly configured making further configuration rare.© Rick Strahl, West Wind Technologies, 2005-2011Posted in Windows HTTP .NET FoxPro
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