The network protocols such as UDP, SCTP, TCP and DCCP identify a source and destination and source port number in the packet heads. Port number is a 16 bit unidentified integer which has a range of 0 to 65535. The process associated with sending and receiving data by using any particular port is known as binding. This means that the network port would listen to the data packet whose port destination number IP address matches. In UNIX operating systems only authorize users can create ports with 0 to 1023 .this stops unauthorized users to provide system services. The port numbers are part of transport layer protocols and are contained in their heads. These ports can be identified by all network computers as well as the sender and the receiver. Firewall is usually used to differentiate in the sources and destination port numbers. The association to the network protocols is made with the help of the sockets. It is software configuration which is used as the transport stop point. This socket is created for supporting operating system. It contains a port number and an IP address. The sockets can be half duplex or full duplex at a time. Port scanning is an essential in order to connect to a number of services over a single computer. Port scanning also helps to identify possible crackers attack and provide possible security.
Most common TCP/UDP Port List
The ports are assigned by IANA (internet assigned numbers authority). The list of most commonly used TCP ports are 1/TCP, UDP, 2/TCP, UDP up to 19/TCP, UDP, 20/TCP, UDP, 21/TCP, 22/TCP,UDP,23/TCP, 25/TCP, 34/TCP,UDP to up to 42/TCP,UDP,43/TCP,47/TCP, 49/TCP,UDP to 56/TCP,UDP .135/TCP,UDP, this is a Microsoft end point mapper or a locator service . This port is remotely used to mange the services like DHCP server, DNS server and DCOMS, 137/TCP, UDP up to 158/TCP, UDP. 158/TCP, UDP is making use of distributed mail service protocol. 161/UDP, 161/TCP, UDP to 264/TCP, UDP are some other number of network ports. This series is up to 1 to 1023. Some of the ports are not official now like 42/TCP, UDP, 56/TCP, UDP, 90/TCP, UDP, 370/TCP, UDP, 456/TCP, UDP, 752/TCP, UDP, 760/TCP, UDP and 901/TCP, UDP.
The Port Number Ranges
The port numbers have three ranges well known ports, dynamic ports and registered ports. The well known ports range form 0 to 1023. The registered ports start from1024 to 49151. 49152 to 65535 ports are known as private or dynamic ports. The well known port numbers are associated by running the programs executed by restricted users. Ports are worn in the TCP [RFC793] to give name to the ends of logical associations which carry extended conversations. For providing services to unidentified callers, a service contact port is recognized. This list indicates the port used by the server procedure as its contact port. The contact port is also termed as the” Well known port”. The Registered Ports are nominated by the IANA most systems use ordinary user processes or programs executed by ordinary clients. In order to provide services to anonymous callers, a service contact port is often defined. This list stipulates the port used by the server process as a contact port.
There is a long list of registered ports but some important ports are 1025/TCP,1026/TCP,1027/TCP,1029/TCP,111/UDP,1167/UDP,1234/UDP, 1236/TCP,2190/UDP, 2200/UDP,2221/TCP,2223/UDP,2301/TCP,2303/UDP, 2305/UDP,2381/TCP,2401/TCP,2977/TCP up to3025/TCP,3537/TCP,UDP4000/TCP,UDP,5555/TCP,6902-6968/TCP,UDP,6960-6999/TCP,UDP,9420-9422/TCP,27000/TCP-27009/TCP,47808/TCP,UDP, 49151/TCP,UDP.