The Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) each use port numbers for their communication channels. The ports numbered 0 through 1023 are the well-known system ports, reserved for special uses.
Port 0 is not used for TCP/UDP communication although it used as a network programming construct.
The Breakdown of Other System Ports
- (TCP) TCPMUX - TCP Port Service Multiplexer. Allows any of multiple TCP services to be contacted by their service name. See RFC 1078.
- (TCP) Management Utility. Formerly used by the Compressnet product, for compression of TCP WAN traffic.
- (TCP) Compression Process. Formerly used by Compressent for compression of TCP WAN traffic.
- (TCP/UDP) Unassigned
- (TCP/UDP) Remote Job Entry. Mechanism for executing batch jobs remotely. See RFC 407.
- (TCP/UDP) Unassigned
- (TCP/UDP) Echo. When enabled for debugging purposes, returns to the source any data received. See RFC 862.
- (TCP/UDP) Unassigned
- (TCP/UDP) Discard. When enabled for debugging purposes, throws away any data received with no response sent. See RFC 86.
- (TCP/UDP) Unassigned
- (TCP) Active Users. Unix TCP systat. See RFC 866.
- (TCP/UDP) Unassigned
- (TCP/UDP) Daytime. See RFC 867.
- (TCP/UDP) Unassigned
- (TCP/UDP) Unassigned. Formerly reserved for Unix netstat.
- (TCP/UDP) Unassigned.
- (TCP/UDP) Quote of the Day. For Unix qotd. See RFC 865.
- (TCP) Message Send Protocol (formerly) and Remote Write Protocol. (UDP) Remote Wire Protocol. See RFC 1312 and RFC 1756.
- (TCP/UDP) Character Generator Protocol. See RFC 864.
- (TCP) File Transfer. For FTP data.
- (TCP) File Transfer. For FTP control.
- (TCP) SSH Remote Login Protocol. (UDP) pcAnywhere.
- (TCP) Telnet
- (TCP/UDP) For private mail systems.
- (TCP) Simple Mail Transfer Protocol (SMTP). See RFC 821.
- (TCP/UDP) Unassigned
- (TCP/UDP) ESMTP. POP mail service of SLMail.
- (TCP/UDP) Unassigned
- (TCP/UDP) MSG ICP.
- (TCP/UDP) Unassigned
- (TCP/UDP) MSG Authentication
- (TCP/UDP) Unassigned
- (TCP/UDP) Display Support Protocol
- (TCP/UDP) Unassigned
- (TCP/UDP) For private printer servers.
- (TCP/UDP) Unassigned
- (TCP/UDP) Time Protocol. See RFC 868.
- (TCP/UDP) Route Access Protocol (RAP). See RFC 1476.
- (UDP) Resource Location Protocol. See RFC 887.
- (TCP/UDP) Unassigned
- (TCP/UDP) Graphics
- (UDP) Host Name Server - Microsoft WINS
- (TCP) WHOIS. Also known as NICNAME. RFC 954.
- (TCP) MPM FLAGS Protocol
- (TCP) Message Processing Module (receive)
- (TCP) Message Processing Module (send)
- (TCP/UDP) NI FTP
- (TCP/UDP) Digital Audit Daemon
- (TCP) Login Host Protocol. Also known as TACACS. See RFC 927 and RFC 1492.
- (TCP/UDP) Remote Mail Checking Protocol (RMCP). See RFC 1339.
- (TCP/UDP) IMP Logical Address Maintenance
- (TCP/UDP) XNS Time Protocol
- (TCP/UDP) Domain Name Server (DNS)
- (TCP/UDP) XNS Clearinghouse
- (TCP/UDP) ISI Graphics Language
- (TCP/UDP) XNS Authentication
- (TCP/UDP) private terminal access. For example, TCP Mail Transfer Protocol (MTP). See RFC 772 and RFC 780.
- (TCP/UDP) XNS Mail
- (TCP/UDP) private file services. For example, NFILE. See RFC 1037.
- (TCP/UDP) Unassigned
- (TCP/UDP) NI Mail
- (TCP/UDP) ACA Services
- (TCP/UDP) Whois and Network Information Lookup Service. Also known as Whois++. See RFC 1834.
- (TCP/UDP) Communications Integrator
- (TCP/UDP) TACACS Database Service
- (TCP/UDP) Oracle SQL*NET
- (TCP/UDP) Bootstrap Protocol Server. (UDP) Unofficially, Dynamic Host Configuration Protocol (DHCP) servers use this port.
- (TCP/UDP) Bootstrap Protocol Client (BOOTP). See RFC 951. (UDP) Unofficially, DHCP clients use this port.
- (TCP/UDP) Trivial File Transfer Protocol (TFTP). See RFC 906 and RFC 1350.
- (TCP/UDP) Gopher. See RFC 1436.
- (TCP/UDP) Remote Job Service
- (TCP/UDP) Remote Job Service
- (TCP/UDP) Remote Job Service
- (TCP/UDP) Remote Job Service
- (TCP/UDP) private dial-out services
- (TCP/UDP) Distributed External Object Store
- (TCP/UDP) private remote job execution services
- (TCP/UDP) Vettcp Service
- (TCP/UDP) Finger User Information Protocol. See RFC 1288.
- (TCP) Hypertext Transfer Protocol (HTTP). See RFC 2616.
- (TCP/UDP) HOSTS2 Name Server
- (TCP/UDP) XFER Utility
- (TCP/UDP) MIT ML Device
- (TCP/UDP) Common Trace Facility
- (TCP/UDP) MIT ML Device
- (TCP/UDP) Micro Focus COBOL
- (TCP/UDP) private terminal links
- (TCP/UDP) Kerberos Network Authentication Service. See RFC 1510.
- (TCP/UDP) SU/MIT Telnet Gateway
- (TCP/UDP) DNSIX Security Attribute Token Map
- (TCP/UDP) MIT Dover Spooler
- (TCP/UDP) Network Printing Protocol
- (TCP/UDP) Device Control Protocol
- (TCP/UDP) Tivoli Object Dispatcher
- (TCP/UDP) SUPDUP Display Protocol. See RFC 734.
- (TCP/UDP) DIXIE Protocol. See RFC 1249.
- (TCP/UDP) Swift Remote Virtual File Protocol
- (TCP/UDP) TAC News. Unofficially used today by Linux utility linuxconf.
- (TCP/UDP) Metagram Relay