| Port Number/Layer | Name | Description |
|---|
| 1 | tcpmux | TCP Port Service Multiplexer |
| 5 | rje | Remote Job Entry |
| 7 | echo | Echo service |
| 9 | discard | Null service for connection testing |
| 11 | systat | System status for listing connected ports |
| 13 | daytime | Sends date and time to requesting host |
| 17 | qotd | Sends daily quotes to connected hosts |
| 18 | msp | Message Send Protocol |
| 19 | chargen | Character Generator service; sends endless character stream |
| 20 | ftp-data | FTP data port |
| 21 | ftp | File Transfer Protocol (FTP) port; sometimes used by File Service Protocol (FSP) |
| 22 | ssh | Secure Shell (SSH) service |
| 23 | telnet | Telnet service |
| 25 | smtp | Simple Mail Transfer Protocol (SMTP) |
| 37 | time | Time Protocol |
| 39 | rlp | Resource Location Protocol |
| 42 | nameserver | Internet Name Service |
| 43 | nicname | WHOIS directory service |
| 49 | tacacs | Terminal Access Controller Access Control System for TCP/IP-based authentication and access |
| 50 | re-mail-ck | Remote Mail Check Protocol |
| 53 | domain | Domain Name Service (e.g., BIND) |
| 63 | whois++ | WHOIS++, extended WHOIS service |
| 67 | bootps | Bootstrap Protocol (BOOTP) service; also used by Dynamic Host Configuration Protocol (DHCP) service |
| 68 | bootpc | Bootstrap (BOOTP) client; also used by Dynamic Host Configuration Protocol (DHCP) client |
| 69 | tftp | Trivial File Transfer Protocol (TFTP) |
| 70 | gopher | Gopher Internet document search and retrieval |
| 71 | netrjs-1 | Remote Job Service |
| 72 | netrjs-2 | Remote Job Service |
| 73 | netrjs-3 | Remote Job Service |
| 73 | netrjs-4 | Remote Job Service |
| 79 | finger | Finger service for user contact information |
| 80 | http | Hypertext Transfer Protocol (HTTP) for World Wide Web (WWW) service |
| 88 | kerberos | Kerberos network authentication system |
| 95 | supdup | Telnet protocol extension |
| 101 | hostname | Hostname service on SRI-NIC machines |
| 102 | iso-tsap | ISO Development Environment (ISODE) network applications |
| 105 | csnet-ns | Mailbox Name Server; also used by CSO Name Server |
| 107 | rtelnet | Remote Telnet |
| 109 | pop2 | Post Office Protocol version 2 |
| 110 | pop3 | Post Office Protocol version 3 |
| 111 | sunrpc | Remote Procedure Call (RPC) protocol for remote command execution, used by Network File System (NFS) |
| 113 | auth | Authentication and identification protocol |
| 115 | sftp | Secure File Transfer Protocol (SFTP) service |
| 117 | uucp-path | Unix-to-Unix Copy Protocol (UUCP) path service |
| 119 | nntp | Network News Transfer Protocol (NNTP) for USENET discussion system |
| 123 | ntp | Network Time Protocol (NTP) |
| 137 | netbios-ns | NETBIOS Name Service used by Samba in Red Hat Enterprise Linux |
| 138 | netbios-dgm | NETBIOS Datagram Service used by Samba in Red Hat Enterprise Linux |
| 139 | netbios-ssn | NETBIOS Session Service used by Samba in Red Hat Enterprise Linux |
| 143 | imap | Internet Message Access Protocol (IMAP) |
| 161 | snmp | Simple Network Management Protocol (SNMP) |
| 162 | snmptrap | SNMP traps |
| 163 | cmip-man | Common Management Information Protocol (CMIP) |
| 164 | cmip-agent | Common Management Information Protocol (CMIP) |
| 174 | mailq | MAILQ |
| 177 | xdmcp | X Display Manager Control Protocol |
| 178 | nextstep | NeXTStep window server |
| 179 | bgp | Border Gateway Protocol |
| 191 | prospero | Clifford Neuman's Prospero service |
| 194 | irc | Internet Relay Chat (IRC) |
| 199 | smux | SNMP UNIX Multiplexer |
| 201 | at-rtmp | AppleTalk routing |
| 202 | at-nbp | AppleTalk name binding |
| 204 | at-echo | AppleTalk echo service |
| 206 | at-zis | AppleTalk zone information |
| 209 | qmtp | Quick Mail Transfer Protocol (QMTP) |
| 210 | z39.50 | NISO Z39.50 database |
| 213 | ipx | Internetwork Packet Exchange (IPX), a datagram protocol commonly used in Novell Netware environments |
| 220 | imap3 | Internet Message Access Protocol version 3 |
| 245 | link | LINK |
| 347 | fatserv | Fatmen server |
| 363 | rsvp_tunnel | RSVP tunnel |
| 369 | rpc2portmap | Coda file system port mapper |
| 370 | codaauth2 | Coda file system authentication service |
| 372 | ulistproc | UNIX Listserv |
| 389 | ldap | Lightweight Directory Access Protocol (LDAP) |
| 427 | svrloc | Service Location Protocol (SLP) |
| 434 | mobileip-agent | Mobile Internet Protocol (IP) agent |
| 435 | mobilip-mn | Mobile Internet Protocol (IP) manager |
| 443 | https | Secure Hypertext Transfer Protocol (HTTP) |
| 444 | snpp | Small Network Paging Protocol |
| 445 | microsoft-ds | Server Message Block (SMB) over TCP/IP |
| 464 | kpasswd | Kerberos password and key change service |
| 468 | photuris | Photuris session key management protocol |
| 487 | saft | Simple Asymmetric File Transfer (SAFT) protocol |
| 488 | gss-http | Generic Security Service (GSS) for HTTP |
| 496 | pim-rp-disc | Rendezvous Point Discovery (RP-DISC) for Protocol Independent Multicast (PIM) service |
| 500 | isakmp | Internet Security Association and Key Management Protocol (ISAKMP) |
| 535 | iiop | Internet Internal Object Request Protocol (IIOP) |
| 538 | gdomap | GNUstep Distributed Object Mapper (GDOMAP) |
| 546 | dhcpv6-client | Dynamic Host Configuration Protocol (DHCP) version 6 client |
| 547 | dhcpv6-server | Dynamic Host Configuration Protocol (DHCP) version 6 server |
| 554 | rtsp | Real-time Stream Protocol (RTSP) |
| 563 | nntps | Through security socket layer network News Transfer Protocol (NNTPS) |
| 565 | whoami | whoami |
| 587 | submission | Mail message submission agent (MSA) |
| 610 | npmp-local | Network peripheral management protocol (NPMP) local/distributed queuing system (DQS) |
| 611 | npmp-gui | Network peripheral management protocol (NPMP) GUI/distributed queuing system (DQS) |
| 612 | hmmp-ind | HMMP indication/DQS |
| 631 | ipp | Internet Printing Protocol (IPP) |
| 636 | ldaps | Through security socket layer lightweight directory access protocol (LDAPS) |
| 674 | acap | Application configuration access protocol (ACAP) |
| 694 | ha-cluster | Used with high availability clusters' heartbeat service |
| 749 | kerberos-adm | Kerberos version 5 (v5) of "kadmin" database administration |
| 750 | kerberos-iv | Kerberos version 4 (v4) service |
| 765 | webster | Web dictionary |
| 767 | phonebook | Web phone book |
| 873 | rsync | rsync file transfer service |
| 992 | telnets | Through security socket layer Telnet (TelnetS) |
| 993 | imaps | Through security socket layer internet message access protocol (IMAPS) |
| 994 | ircs | Through security socket layer internet Relay Chat (IRCS) |
| 995 | pop3s | Through security socket layer mail service version 3 (POPS3) |
