url: Proxies
5.2 Proxies and Gatewaying
==========================
Proxy servers are commonly used to provide gateways through firewalls or
as caches serving some more-or-less local network. Each protocol (HTTP,
FTP, etc.) can have a different gateway server. Proxying is
conventionally configured commonly amongst different programs through
environment variables of the form ‘PROTOCOL_proxy’, where PROTOCOL is
one of the supported network protocols (‘http’, ‘ftp’ etc.). The
library recognizes such variables in either upper or lower case. Their
values are of one of the forms:
• ‘HOST:PORT’
• A full URL;
• Simply a host name.
The ‘NO_PROXY’ environment variable specifies URLs that should be
excluded from proxying (on servers that should be contacted directly).
This should be a comma-separated list of hostnames, domain names, or a
mixture of both. Asterisks can be used as wildcards, but other clients
may not support that. Domain names may be indicated by a leading dot.
For example:
NO_PROXY="*.aventail.com,home.com,.seanet.com"
says to contact all machines in the ‘aventail.com’ and ‘seanet.com’
domains directly, as well as the machine named ‘home.com’. If
‘NO_PROXY’ isn’t defined, ‘no_PROXY’ and ‘no_proxy’ are also tried, in
that order.
Proxies may also be specified directly in Lisp.
-- User Option: url-proxy-services
This variable is an alist of URL schemes and proxy servers that
gateway them. The items are of the form
‘(SCHEME . HOST:PORTNUMBER)’, says that the URL SCHEME is gatewayed
through PORTNUMBER on the specified HOST. An exception is the
pseudo scheme ‘"no_proxy"’, which is paired with a regexp matching
host names not to be proxied. This variable is initialized from
the environment as above.
(setq url-proxy-services
'(("http" . "proxy.aventail.com:80")
("no_proxy" . "^.*\\(aventail\\|seanet\\)\\.com")))
Info Catalog
url: Disk Caching
url: General Facilities
url: Gateways in general