Find a Port to Hack

What is a port scanner?

A port scanner is a handy tool that scans a computer looking for active ports. With this utility, a potential “hacker” can figure out what services are available on a targeted computer from the responses the port scanner receives. Take a look at the list below for reference.
Starting Scan.

Target Host: www.yourcompany.com
TCP Port :7 (echo)
TCP Port :9 (discard)
TCP Port :13 (daytime)
TCP Port :19 (chargen)
TCP Port :21 (ftp)
TCP Port :23 (telnet)
TCP Port :25 (smtp)
TCP Port :37 (time)
TCP Port :53 (domain)
TCP Port :79 (finger)
TCP Port :80 (www)
TCP Port :110 (pop)
TCP Port :111 (sunrpc)
Finished.

Scanning for open ports is done in two ways. The first is to scan a single IP address for open ports. The second is to scan
a range of IP address to find open ports.

Try to think about this like calling a single phone-number of say 555-4321 and asking for every extension available. In relation to scanning, the phone-number is equivalent to the IP address and the extensions to open ports.

Scanning a range of IP address is like calling every number between 555-0000 to 555-9999 and asking for every extension available at every number.