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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.
UDP is a simple message-oriented transport layer protocol that is documented in RFC 768.Although UDP provides integrity verification (via checksum) of the header and payload, [4] it provides no guarantees to the upper layer protocol for message delivery and the UDP layer retains no state of UDP messages once sent.
In such applications, old messages quickly become useless, so that getting new messages is preferred to resending lost messages. As of 2017 such applications have often either settled for TCP or used User Datagram Protocol (UDP) and implemented their own congestion-control mechanisms, or have no congestion control at all. While being useful for ...
A packet-switched network transmits data that is divided into units called packets.A packet comprises a header (which describes the packet) and a payload (the data). The Internet is a packet-switched network, and most of the protocols in this list are designed for its protocol stack, the IP protocol suite.
The protocols in use today in this layer for the Internet all originated in the development of TCP/IP. In the OSI model the transport layer is often referred to as Layer 4, or L4, [2] while numbered layers are not used in TCP/IP. The best-known transport protocol of the Internet protocol suite is the Transmission Control Protocol (TCP).
Socket often refers specifically to an internet socket or TCP socket. An internet socket is minimally characterized by the following: local socket address, consisting of the local IP address and (for TCP and UDP, but not IP) a port number; protocol: A transport protocol, e.g., TCP, UDP, raw IP.
Protocol data units for the Internet protocol suite are: . The transport layer PDU is the TCP segment for TCP, and the datagram for UDP; The Internet layer PDU is the packet.; The link layer PDU is the frame.
TCP timestamps, defined in RFC 1323 in 1992, can help TCP determine in which order packets were sent. TCP timestamps are not normally aligned to the system clock and start at some random value. Many operating systems will increment the timestamp for every elapsed millisecond; however, the RFC only states that the ticks should be proportional.