URL : default values

From    escience/nm   

used in a web browser   http://escience:80/nm

within a specified network ( ANU, anu.edu.au is the ISP)      http://escience.anu.edu.au:80/nm

Server : no suffix ? it must be a directory : http://escience.anu.edu.au:80/nm/

Server : is there a file named index.html  in that directory ? yes ? Let's return that one :

http://escience.anu.edu.au:80/nm/index.html

And an additional step, not usual

Browser : Oh ? That file asks me to load another one instead ? let's do it :

to    http://escience.anu.edu.au/lecture/comp1710/index.en.html

NB : About directory and file naming, lots of things are possible, but if you don't want to bother remembering more:

• never use spaces

• everything lower case (not compulsory)

• just alphanumeric characters, '.', '-'. and '_'

• suffix for the filename (.html for HTML files, .txt for text files)

The general form of an URL has four parts

1. A scheme followed by a colon.
   • Invokes a TCP/IP-based application level protocol
   • Schemes are: http, ftp, news, mailto, file, telnet.
     
2. A server name.
   • A // followed by the host name or IP address of the server
   • Not needed if the server is the default
     • news server
     • mail server
3. An optional port number. Standard or default port numbers are:

   ftp	*
   telnet	23
   smtp	25
   gopher	70
   http	80
   nntp	119
   SSL	443

4. A path.
   • Consisting of folders and/or files.
   • May include a file extension which identifies the type of document.
   • May also include a QUERY_STRING with arguments.

   * Ftp uses port 20 for data and port 21 for flow control.

Source : http://www.pierobon.org/iis/urlparts.htm