A domains may be a class A, B, or C networks, which determines the number of hosts IP addresses available. Class C networks may have 254 hosts. It is in the large domain called 'edu' which is then divided into the sub-domain 'csubak'. For simplicity, the domain name is 'csubak.edu'. The convention follows the Unix operating system, since the Internet began with Unix computers.
Filenames are case sensitive.
Port Numbers Port numbers are used on the Internet for technical connection purposes. For instance, the Telnet process which usually uses port 23 on a computer, may have specialized non-standard ports available for connection. If you don't specify a port, the default port is used.