.NET & XML

Network Access Through a Web Proxy

Another useful feature of the WebRequest class is its ability to read data through a web proxy. A web proxy is a server located on the network between your code and a web server. Its job is to intercept all traffic headed for the web server and attempt to fulfill as many requests as it can without contacting the web server. If a web proxy cannot fulfill a request itself, it forwards the request to the web server for processing.

Web proxies serve two primary purposes:

Improving performance

A proxy server can cache data locally to speed network performance. Rather than sending two identical requests from different clients to the same web resource, the results of the first request are saved, and sent back to any other clients requesting the same data. Typical web proxies have configurable parameters that control how long cached data is retained before new requests are sent on to the web server. The HTTP protocol can also specify this cache refresh period. Many large online services, such as America Online, use caching to improve their network performance.

Filtering

A proxy server can be used to filter access to certain sites. Filtering is usually used by businesses to prevent employees from accessing web sites that have no business-related content, or by parents to prevent children from accessing web sites that may have material they believe is inappropriate. Filters can be as strict or loose as necessary, preventing access to entire IP subnets ...