List of TCP and UDP port numbers. This is a list of TCP and UDP port numbers used by protocols of the transport layer of the Internet protocol suite for the establishment of host to host connectivity. Originally, port numbers were used by the Network Control Program NCP in the ARPANET for which two ports were required for half duplex transmission. Later, the Transmission Control Protocol TCP and the User Datagram Protocol UDP needed only one port for full duplex, bidirectional traffic. The even numbered ports were not used, and this resulted in some even numbers in the well known port number range being unassigned. The Stream Control Transmission Protocol SCTP and the Datagram Congestion Control Protocol DCCP also use port numbers. They usually use port numbers that match the services of the corresponding TCP or UDP implementation, if they exist. The Internet Assigned Numbers Authority IANA is responsible for maintaining the official assignments of port numbers for specific uses. However, many unofficial uses of both well known and registered port numbers occur in practice. Address an issue in which Windows Server 2016 is stuck at the Downloading updates 0 stage when it downloads from Windows Update. Similarly many of the official assignments refer to protocols that were never or are no longer in common use. This article lists port numbers and their associated protocols that have experienced significant uptake. Table legendedit  Official Port is registered with IANA for the application. Unofficial Port is not registered with IANA for the application. Multiple use Multiple applications are known to use this port. Well known portseditThe port numbers in the range from 0 to 1. They are used by system processes that provide widely used types of network services. On Unix like operating systems, a process must execute with superuser privileges to be able to bind a network socket to an IP address using one of the well known ports. Well known ports. Cannot Start Windows Firewall Service Error 1068 Print' title='Cannot Start Windows Firewall Service Error 1068 Print' />Port. TCPUDPDescription. IANA status. 0NANAIn programming APIs not in communication between hosts, requests a system allocated dynamic port4NA0. Reserved. Reserved. Reserved. Official. TCPAssigned. TCP Port Service Multiplexer TCPMUX. Historic. Both TCP and UDP have been assigned to TCPMUX by IANA,1 but by design only TCP is specified. Official. Reserved. Reserved. Unassigned. Official. TCPUDPRemote job entry. Official. 6Reserved. Reserved. Unassigned. Official. 7TCPUDPEcho Protocol67Official. Reserved. Reserved. Unassigned. Official. UDPDiscard Protocol9Official. UDPWake on LAN1. Unofficial. Reserved. Reserved. Unassigned. Official. TCPUDPActive Users systat service1. Official. 12. Reserved. Reserved. Unassigned. Here in this post we have explained the proper solution for Windows Update error. Follow the following steps how to fix windows update error. SmartPCFixer is a fully featured and easytouse system optimization suite. With it, you can clean windows registry, remove cache files, fix errors, defrag disk. Hi ZZCheetahZZ, Regarding the The Audio service is not running issue, please first try start the Windows Audio service by the steps below 1. A complete list of system error codes, from code 1 through 15841. Here, too, are meanings for each system error code, plus other ways they may appear. Error 678 is an error that is reported when a remote system does not respond correctly when an attempt is made to connect to the Internet. The Error 678 message. Cannot Start Windows Firewall Service Error 1068 Print' title='Cannot Start Windows Firewall Service Error 1068 Print' />Official. TCPUDPDaytime Protocol1. Official. 14. Reserved. Reserved. Unassigned. Official. 15. TCPUDPPreviously netstat service11. Unofficial. 16. Reserved. Reserved. Unassigned. Official. 17. TCPUDPQuote of the Day QOTD1. Official. 18. TCPUDPMessage Send Protocol1. Official. 19. TCPUDPCharacter Generator Protocol CHARGEN1. Official. 20. Assigned. Need For Speed Underground Disk 2 Cracking on this page. File Transfer Protocol FTP data transfer7Official. Assigned. File Transfer Protocol FTP control command781. Official. 22. UDPSecure Shell SSH,7 secure logins, file transfers scp, sftp and port forwarding. Official. 23. TCPAssigned. Telnet protocolunencrypted text communications72. Official. 25. TCPAssigned. Simple Mail Transfer Protocol SMTP,72. Official. 26. Reserved. Reserved. Unassigned. Official. 37. TCPUDPTime Protocol2. Official. 38. TCPUDPRoute Access Protocol RAP2. Official. 39. TCPUDPResource Location Protocol RLP2. Official. 40. Reserved. Reserved. Unassigned. Official. 42. TCPUDPHost Name Server Protocol2. Official. 43. TCPUDPWHOIS protocol2. Official. 49. TCPUDPTACACS Login Host protocol2. Official. 50. TCPUDPRemote Mail Checking Protocol3. Official. 51. Reserved. Official. 51. TCPUDPPreviously Interface Message Processor logical address managementcitation neededUnofficial. TCPUDPXerox Network Systems XNS Time ProtocolimportanceOfficial. TCPUDPDomain Name System DNS7Official. TCPUDPXerox Network Systems XNS clearinghouseimportanceOfficial. TCPUDPXerox Network Systems XNS authenticationimportanceOfficial. TCPUDPAny private terminal accessfurther explanation neededOfficial. TCPUDPXerox Network Systems XNS MailimportanceOfficial. Assigned. UDPBootstrap Protocol BOOTP server 7 also used by Dynamic Host Configuration Protocol DHCPOfficial. Assigned. UDPBootstrap Protocol BOOTP client 7 also used by Dynamic Host Configuration Protocol DHCPOfficial. Assigned. UDPTrivial File Transfer Protocol TFTP73. Official. 70. TCPUDPGopher protocol3. Official. 717. 4TCPUDPNETRJS protocol3. Official. 75. TCPUDPAny private dial out servicefurther explanation neededOfficial. TCPUDPAny private Remote job entryfurther explanation neededOfficial. TCPAssigned. Finger protocol73. Official. 80. UDP4. Hypertext Transfer Protocol HTTP74. Official. 80. UDPQUIC from Chromium for HTTPcitation neededUnofficial. NANAUnassigned. Official. TCPTor. Parkonion routingverification neededUnofficial. UDPTor. Park controlverification neededUnofficial. Any private terminal linkfurther explanation neededOfficial. TCPAssigned. Kerberos74. Official. 90. TCPUDPdnsix Do. D Network Security for Information Exchange Securit sic Attribute Token MapimportanceOfficial. TCPUDPPoint. Cast dotcom1third party source neededUnofficial. TCPWIP message protocolverification neededUnofficial. NANAUnassigned with known unauthorized usefurther explanation needed1Official. TCPUDPNIChost name. Official. 10. 2TCPUDPISO Transport Service Access Point TSAP Class 0 protocol 4. Official. 10. 4TCPUDPDigital Imaging and Communications in Medicine DICOM also port 1. Official. 10. 5TCPUDPCCSO Nameserver4. Official. 10. 7TCPUDPRemote User Telnet Service RTelnet4. Official. 10. 8TCPUDPIBM Systems Network Architecture SNA gateway access server. Official. 10. 9TCPUDPPost Office Protocol, version 2 POP25. Official. 11. 0TCPAssigned. Post Office Protocol, version 3 POP375. Official. 11. 1TCPUDPOpen Network Computing Remote Procedure Call ONC RPC, sometimes referred to as Sun RPCOfficial. TCPUDPmcidas Mc. IDAS Data Transmission ProtocolOfficial. TCPIdent, authentication serviceidentification protocol,75. IRC servers to identify users. Official. 11. 3TCPAssigned. Authentication Service auth, the predecessor to identification protocol. Used to determine a users identity of a particular TCP connection. Official. 11. 4NANAUnassigned deprecated since June 2. Official. 11. 5TCPUDPSimple File Transfer Protocol75. Official. 11. 7TCPUDPUUCP Mapping Project path servicecitation neededOfficial. TCPUDPStructured Query Language SQL ServicesJargonOfficial. TCPAssigned. Network News Transfer Protocol NNTP,7 retrieval of newsgroup messages5. Official. 12. 3Assigned. UDPNetwork Time Protocol NTP, used for time synchronization7Official. TCPUDPFormerly Unisys Unitary Login, renamed by Unisys to NXEdit. Used by Unisys Programmers Workbench for Clearpath MCP, an IDE for Unisys MCP software development. Official. 13. 5TCPUDPDCEendpoint resolution. Official. 13. 5TCPUDPMicrosoft EPMAP End Point Mapper, also known as DCERPC Locator service,5. DHCP server, DNS server and WINS. Also used by DCOMOfficial. Assigned. UDPNet. BIOS Name Service, used for name registration and resolution5. Official. 13. 8TCPUDPNet. BIOS Datagram Service75. Official. 13. 9TCPAssigned. Net. BIOS Session Service5. Official. 14. 3TCPAssigned.