The following function checks to see how many dots are in the hostname. If there are any dots in the hostname, make a connection via proxy. If there are no dots in the hostname, make a direct connection.
This is another way to determine connection types based on hostname characteristics. The dnsDomainLevels function returns an integer equal to the number of dots in the hostname. Example Specify days of the week to connect via proxy, other days connect direct. The following function determines the connection type by specifying days of the week that are appropriate for a proxy. Days that do not fall between these parameters use a direct connection.
This function could be useful in situations where you might want to use a proxy when traffic is heavy and allow a direct connection when traffic is light. The weekdayRange day1 [,day2] [,GMT] function returns whether the current system time falls within the range specified by the parameters day1, day2, and GMT. Only the first parameter is required. Example Load Balancing with a simple Math function. Contents Question:.
Question: What is a Proxy Pac file, and are there any examples? The isInNet , isResolvable , and dnsResolve functions query a DNS server References to Object Model objects, properties, or methods cause the proxy auto-configuration file to fail silently.
For example, the references window. Example 1: Local hosts connect direct, all others connect via proxy The following function checks to see whether the hostname is a local host, and if it is, whether the connection is direct.
Not all requests to local webservers are done using just hostnames Example 2: Hosts inside the firewall connect direct, outside local servers connect via proxy The following function checks to see whether the host is either a "plain" hostname meaning the domain name is not included or part of a particular domain.
The dnsDomainIs function returns true if the domain of the hostname matches the domain given. Example 5: Determine connection type based on host domain The following function specifies a direct connection if the host is local. Example 6: Determine connection type based on protocol being used The following function extracts the protocol being used and makes a proxy selection accordingly.
Example 7: Determine proxy setting by checking to see if hostname matches IP address The following function makes a proxy selection by translating the hostname into an IP address and comparing it to a specified string. The proxyUser object uses the user object to store data. The proxyUser can access all properties of the user object. Fourth, access the firstName and lastName properties of the user object via the proxyUser object:.
When you access a property of the user object via the proxyUser object, the get method in the handler object is called. Fifth, if you modify the original object user , the change is reflected in the proxyUser :. Similarly, a change in the proxyUser object will be reflected in the original object user :.
The get trap is fired when a property of the target object is accessed via the proxy object. Typically, the configuration script is a JavaScript file that contains logic to determine whether to use a proxy and what proxy to use for a given target resource. The reply to this message contains the URL of the configuration script. You can try this in your own network. If you don't see this, it might be because the network administrator uses custom configuration files with the Internet Explorer Administration Kit IEAK or some other nonstandard configuration.
The second step is to download the configuration script from the URL and run the script. You pass the URL into the function as well as the host to which you would like to connect, and the function returns one or more proxy servers to use. The user agent should try the proxy servers in the order returned. Note that the user agent can get different script content each time the script is downloaded.
This might happen because the network administrator has updated the script to reflect the new proxy servers she has added to the pool of proxy servers. The script can contain logic to determine what proxy to use based on the day, time, subnet of the client machine, and the target URL. By selecting automatic configuration, user agents detect the configuration script URL, download and run the script to automatically determine what proxy to use.
You can see that a lot of stuff happens behind the scenes to make automatic configuration work. The benefit is that no manual proxy configuration of clients is required. WebProxy and System.
GlobalProxySelection classes. When you install the. This means that when you access the GlobalProxySelection. Select property, the proxy instance returned will contain the settings from the registry. One of the issues in the. Only the static portion of the proxy settings are read.
However, if the default proxy settings in Internet Explorer are configured for automatic detection and static settings are not populated, the result is that Internet Explorer seems to download the resources correctly, while applications using the. The WebRequest class then tries to connect to the resource directly bypassing any proxy to the target resource. Since external names can't be resolved in a protected network, you get a "name not resolved" exception thrown back at you.
NET as shown in Figure 2. On the left side is an Internet Explorer browser control that can automatically detect proxy settings and is able to display the Web methods properly. On the right side, the. In order to fix this issue, you have three options. The first is to create a WebProxy instance with a specific proxy name and assign it to the WebRequest. Proxy property. The second option is to enter the static settings in Internet Explorer, so the.
NET Framework will read those settings. The third option is to use the configuration either Machine. The other issue with. In other words, only the DefaultConnectionSettings value is read irrespective of the current active connection. Imagine a scenario in which you are using a remote access connection to your corporate network from home. When you are connected to the corporate network, your requests should be routed through the proxy in your corporate network.
But since the. Long-running applications have another issue with. Imagine that the static proxy you entered in Internet Explorer is down and your friendly helpdesk person gave you another proxy name to try.
After you enter the new proxy name, you would expect your managed app to pick up the new proxy settings. But it doesn't. Once the GlobalProxySelection class reads the proxy settings, they are cached per app domain, and they are not refreshed. The only solution is to reload the app domain, which in most applications means you need to restart the app. Many users wonder why their code that calls a Web service works fine on a console but doesn't work when they drop it in an.
The answer is that the ASP. NET account runs under a different user account than the interactive user. Since there is no easy way to edit the proxy settings for the ASP. NET user in the registry, you need to enter the proxy settings explicitly in the Web. Fear not, however—the. All of the issues I've mentioned with the. In most of the cases, you don't need to think about the proxy configuration any more, which is always a good thing.
Let's drill down a little further, though. Automatic proxy configuration is now fully supported. Once the script location is identified, the script is downloaded, compiled into an in-memory assembly, and then executed in a sandbox app domain where minimal permissions are granted.
In fact, no code access security CAS permissions are granted to the script other than the execution permission. Minimal permissions mean that rogue scripts can't do anything significant other than call the few functions exposed to the script. For a detailed sample of how to host and run your own scripts in a sandbox app domain, see the sidebar, "Hosting the Proxy Script.
Failover is also built in. If auto-detection fails and if you have entered an explicit script location, then that script is downloaded and run. If both fail and if you have a static proxy, then the static proxy is used as a fallback. If all fail, a direct connection to the target URL is attempted. Hosting the Proxy Script. The Microsoft Active Scripting architecture provided a very successful extensibility platform for applications.
An application could expose an object model and host a script engine, which would enable end users to write scripts to customize and extend the application functionality. For the. NET engine to host proxy scripts. Since this is a managed framework, scripts are compiled into an in-memory assembly.
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