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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.
IN: standard DNS class field (this is always IN). SRV: Type of Record (this is always SRV). priority: the priority of the target host, lower value means more preferred. weight: A relative weight for records with the same priority, higher value means higher chance of getting picked. port: the TCP or UDP port on which the service is to be found.
Such a query consists of a clear-text request sent in a single UDP packet from the client, responded to with a clear-text reply sent in a single UDP packet from the server. When the length of the answer exceeds 512 bytes and both client and server support Extension Mechanisms for DNS (EDNS), larger UDP packets may be used. [41]
TCP uses 16-bit port numbers, providing 65,536 possible values for each of the source and destination ports. [17] The dependency of connection identity on addresses means that TCP connections are bound to a single network path; TCP cannot use other routes that multihomed hosts have available, and connections break if an endpoint's address ...
The most common transport protocols that use port numbers are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP); those port numbers are 16-bit unsigned numbers. A port number is always associated with a network address of a host, such as an IP address, and the type of transport protocol used for communication. It ...
The DHCP employs a connectionless service model, using the User Datagram Protocol (UDP). It is implemented with two UDP port numbers for its operations which are the same as for the bootstrap protocol . The server listens on UDP port number 67, and the client listens on UDP port number 68.
Moreover, DNS messages carried by UDP were restricted to 512 bytes, not considering the Internet Protocol (IP) and transport layer headers. [3] Resorting to a virtual circuit transport, using the Transmission Control Protocol (TCP), would greatly increase overhead. This presented a major obstacle to adding new features to DNS.
The use of the Checksum and Source Port fields is optional in IPv4 (light purple background in table). In IPv6 only the Source Port field is optional. If not used, these fields should be set to zero. [7] Source Port: 16 bits This field identifies the sender's port, when used, and should be assumed to be the port to reply to if needed.