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Name service for name registration and resolution (ports: 137/udp and 137/tcp) Datagram distribution service for connectionless communication (port: 138/udp) Session service for connection-oriented communication (port: 139/tcp) NBT implements all of those services.
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.
[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.
A port is a software structure that is identified by the port number, a 16-bit integer value, allowing for port numbers between 0 and 65535. Port 0 is reserved but is a permissible source port value if the sending process does not expect messages in response. The Internet Assigned Numbers Authority (IANA) has divided port numbers into three ...
For TCP, port number 0 is reserved and cannot be used, while for UDP, the source port is optional and a value of zero means no port. A process associates its input or output channels via an internet socket , which is a type of file descriptor , associated with a transport protocol , a network address such as an IP address , and a port number.
On NetBT, the server component uses three TCP or UDP ports: 137 (NETBIOS Name Service), 138 (NETBIOS Datagram Service), and 139 (NETBIOS Session Service). In Microsoft Windows, two vaguely named Windows services implement SMB. The "Server" service (ID: LanmanServer) is in charge of serving shared resources.
The bottom-most protocol in the suite, the Wireless Datagram Protocol (WDP), functions as an adaptation layer that makes every data network look a bit like UDP to the upper layers by providing unreliable transport of data with two 16-bit port numbers (origin and destination).
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 ...