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This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for bidirectional traffic. TCP usually uses port numbers that match the services of the corresponding UDP implementations, if they exist, and vice versa.
For example, the NetBIOS Name Service (NBNS), running over UDP or TCP port 137, allows any computer to register its hostname with other computers. An attacker could contact any host and claim that they are a particular service the host regularly contacts, such as a file server.
[citation needed] In NBT, the name service operates on UDP port 137 (TCP port 137 can also be used, but rarely is). The name service primitives offered by NetBIOS are: Add name – registers a NetBIOS name. Add group name – registers a NetBIOS "group" name. Delete name – un-registers a NetBIOS name or group name.
This field identifies the sender's port, when used, and should be assumed to be the port to reply to if needed. If the source host is the client, the port number is likely to be an ephemeral port. If the source host is the server, the port number is likely to be a well-known port number from 0 to 1023. [6] Destination Port: 16 bits
In computer networking, a port or port number is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service.
A registered port is a network port designated for use with a certain protocol or application.. Registered port numbers are currently assigned by the Internet Assigned Numbers Authority (IANA) and were assigned by Internet Corporation for Assigned Names and Numbers (ICANN) before March 21, 2001, [1] and were assigned by the Information Sciences Institute (USC/ISI) before 1998.
The program decodes and provides the user with all NetBIOS name packets it receives on UDP port 137. Its many command line options can effectively disable a NetBIOS network and prevent computers from rejoining it. According to Sir Dystic, "NBName can disable entire LANs and prevent machines from rejoining them...nodes on a NetBIOS network ...
An ephemeral port is a communications endpoint of a transport layer protocol of the Internet protocol suite that is used for only a short period of time for the duration of a communication session.