TCP Port Setup

TCP, or Transmission Control Protocol, provides a method of sending data and verifying the correct delivery of that data from client to server. Without a protocol such as TCP data can get lost during transmission or packets can arrive out of order. TCP provides support to detect errors or lost data, and to trigger re-transmission until the data is correctly and completely received.

TCP guarantees the delivery of data and also guarantees that packets will be delivered in the same order in which they were sent. This reliability, however, is achieved at the cost of transmission protocol overhead, which increases the amount of data to be transferred. This can, in some extreme instances, delay of the receipt of the data or exceed the bandwidth of the network.

Port Numbers

The IANA, Internet Assigned Numbers Authority, manages the assignment of TCP and UDP ports from 0-1023.

Port Ids from 0-1023 should not be used. These ports are designated as well-known ports and have been assigned specific functions by the IANA. On most systems these ports can only be used by system processes or processes executed by priveledged users.

Port numbers 1024 - 49151 are called registered ports. They are used as logical connections to carry on long term conversations. On most systems these ports can be used by ordinary user processes. They are not controlled by the IANA, although the IANA registers their use as a convenience to the user community.

Port numbers 49152 - 65535 are called dynamic and/or private ports, and use of these ports should be avoided.

The IANA provides a list of accepted port number assignments that can be found at the following location:

http://www.iana.org/assignments/port-numbers

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