For client-server access the socket needs three things to provide service or ask for service.
Service name (eg. www)
Protocol (eg. http)
Port no (eg. 80)
The service uses protocol and protocol uses port number to provide service at server end and to get service at client end. Services may have same protocol but not the same port number(eg. telnet and ftp)
/etc/protocols - file shows protocols supported by Linux
/etc/services - file shows services supported by Linux
/etc/apache2 - root directory of Apache Web server
/var/www - DocumentRoot(as configured in the file /etc/apache2/sites-available/default )
