While TCP and IP are separate protocols, every computer and network device that is attached to the internet possesses at least a single IP address. In each of the IP addresses, there are a few TCP ports in each of the computers and network devices. TCP uses a numerical identifier for data organization of the endpoints for computer to computer communications. The endpoints are what are referred to as ports.
TCP ports can either be the origin of connections or the recipient of those connections. The numerical identifiers for the ports are called port numbers. The numbers on the ports are maintained by the Internet Assigned Numbers Authority (IANA). The numbers on the ports that are the origin of connections are insignificant. However, the ports that receive connections enable people to trace them. An example of this is DNS which responds on port 53. HTTP on the other hand responds to port 80. The port numbers that have been allocated statistically are called well known port numbers and often go up to 1024.
The port numbers have been divided into categories. There are three categories in all:
1. Well known ports- These are the numbers that fall between 0 and 1023. Administrative privileges are required in the connecting a communications socket to a port under this category of numbers. This applies for the Unix-like operating systems.
2. Registered ports- The numbers in this category range from 1024 to 49151.
3. Dynamic or Private ports- They fall in the range from 49152 to 65535. If numbers are chosen randomly from this category, they are called ephemeral ports. The ports in this category are not allocated permanently to any specific application that is publicly defined.
The Internet Assigned Numbers Authority assigns the well known ports. In most cases, these ports can only be used by system processes. If not these, the ports can be used by programs that are performed by users that are privileged. Ports name the ends of valid connections which carry enduring conversations in TCP. The port allocations can at times be used with UDP. They make use of a limited fraction of port numbers that have been assigned. Previously, the range that now runs to 1023 went only up to 255. Registered ports can be utilized by ordinary users in programs. The use of the ports is registered by Internet Assigned Numbers Authority for the sake of the community’s safety. The ports are also used in the UDP like the well-known numbers.
