C. Proxy Gateways

In late January 1993, Kevin Altis and Lou Montulli proposed and implemented a new proxy service. This service requires the use of environment variables to specify a gateway server/port # to send protocol requests to. Each protocol (HTTP, WAIS, gopher, FTP, etc.) can have a different gateway server. The environment variables are PROTOCOL_proxy, where PROTOCOL is one of the supported network protocols (gopher, file, HTTP, FTP, etc.)

For companies with internal intranets, it will usually be helpful to define a list of hosts that should be contacted directly, not sent through the proxy. The NO_PROXY environment variable controls what hosts are able to be contacted directly. This should be a comma separated list of hostnames, domain names, or a mixture of both. Asterisks can be used as a wildcard. For example:

NO_PROXY=*.aventail.com,home.com,*.seanet.com

tells Emacs/W3 to contact all machines in the aventail.com and seanet.com domains directly, as well as the machine named home.com.

For those adventurous souls who enjoy writing regular expressions, all the proxy settings can be manipulated from Emacs-Lisp. The variable url-proxy-services controls this. This is an assoc list, keyed on the protocol type (HTTP, gopher, etc) in all lowercase. The cdr of each entry should be the ADDRESS of the proxy server to contact, followed by ":" and the port number to use. In the case of the special "no_proxy" entry, it should be a regular expression that matches any hostnames that should be contacted directly.

(setq url-proxy-services
       '(("http"     . "proxy.aventail.com:80")
         ("no_proxy" . "^.*\\(aventail\\|seanet\\)\.com")))

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