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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.
The computer establishing the session attempts to make a TCP connection to port 139 on the computer with which the session is to be established. If the connection is made, the computer establishing the session then sends over the connection a "Session Request" packet with the NetBIOS names of the application establishing the session and the ...
Frequently, the 16th octet, called the NetBIOS Suffix, designates the type of resource, and can be used to tell other applications what type of services the system offers. [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:
This is a list of the IP protocol numbers found in the field Protocol of the IPv4 header and the Next Header field of the IPv6 header. It is an identifier for the encapsulated protocol and determines the layout of the data that immediately follows the header. Both fields are eight bits wide.
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.
They use one of two transport layer protocols: the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). In the tables below, the "Transport" column indicates which protocol(s) the transfer protocol uses at the transport layer. Some protocols designed to transmit data over UDP also use a TCP port for oversight.
The TCP header padding is used to ensure that the TCP header ends, and data begins, on a 32-bit boundary. The padding is composed of zeros. [16] Options have up to three fields: Option-Kind (1 byte), Option-Length (1 byte), Option-Data (variable). The Option-Kind field indicates the type of option and is the only field that is not optional.
Listing open TCP ports that are listening on the local machine. In security parlance, the term open port is used to mean a TCP or UDP port number that is configured to accept packets. In contrast, a port which rejects connections or ignores all packets directed at it is called a closed port. [1]