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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
Routing Network Traffic - Proxies, Redirects and DNS

If you point a domain at web server "X" when it's really hosted on web server "Y", you can either have web server "X" forward the request as a proxy, or you can have server "X" instruct the browser to try "Y" instead ... that's a redirect.

Which is best? A proxy forward hides server "Y" from the browser, but if server "X" has limited bandwidth it will use some of it up. The extra step will also be marginally slower. However, a redirect requires the browser to make a second request of a new server, and server "Y" will not be transparent to the browser.

When you visit a new web site, you'll call up a page based on the domain name ... however, the domain name does NOT tell the structure of the internet how traffic should be routes to the site as it's not based on the network structure - an IP address is required. So the Domain Name Service (DNS) is used to convert the domain name into an IP address, which does reflect the structure.

It works like this - your system (in the imserve.com domain in the example shown here) contacts its DNS server, which knows about DNS servers for its parent and child domains. So it can ask the .com server, which can ask the root server, which can ask .net, which can ask .wellho.net ... and the IP address then gets passed back doen the chain. Having completed that shenanigans, the original machine caches the IP address to save it the bother next time, and uses the IP address directly.

(written 2009-05-01, updated 2009-05-02)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
A052 - Web Application Deployment - Networking - General
  [768] Our new .eu top level domain - (2006-06-19)
  [2150] Routers, Firewalls and multilayer servers - (2009-05-01)
  [2695] TCP v UDP / Client v Server - Python examples - (2010-03-25)

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Variable scope in Java Servlets and other web applications
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Horse's mouth home
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Routers, Firewalls and multilayer servers
Some other Articles
Class Loading and Variable Conversion in Java
My four feet!
What is a JSP tag library?
Routing Network Traffic - Proxies, Redirects and DNS
Variable scope in Java Servlets and other web applications
A very easy JSP (Java Server Page)
An evening excursion to Devizes and Avebury
Using the internet to remotely check for power failure at home (PHP)
Looking for a career change - Physician to Web Site Designer
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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