A network port is a number that identifies one side of a connection between two computers. Computers use port numbers to determine to which process or application a message should be delivered. As network addresses are like street address, port numbers are like suite or room numbers. A network port is a process-specific or an application-specific software construct serving as a communication endpoint, which is used by the Transport Layer protocols of Internet Protocol suite, such as User Diagram Protocol (UDP) and Transmission Control Protocol (TCP).
Network Ports: 0 to 65535, 16bits in binary size. Ports 0 to 1024 are reserved for use by certain privileged services. Source ip:port connects to destination ip:port & transfers data & closes connection. Remote port is predefined & local is dynamic port.
Command:
netstat -lntu
-l= only services which are listening on some port-n= show port number, don't try to resolve the service name-t= tcp ports-u= udp ports-p= name of the program
| PORT | LAYER | NAME | DESCRIPTION |
|---|---|---|---|
| 1 | TCP | tcpmux | TCP port service multiplexer |
| 5 | TCP | rje | Remote Job Entry |
| 7 | TCP | echo | Echo service |
| 9 | TCP | discard | Null service for connection testing |
| 11 | TCP | systat | System Status service for listing connected ports |
| 13 | TCP | daytime | Sends date and time to requesting host |
| 17 | TCP | qotd | Sends quote of the day to connected host |
| 18 | TCP | msp | Message Send Protocol |
| 19 | TCP | chargen | Character Generation service; sends endless stream of characters |
| 20 | TCP | ftp-data | FTP data port |
| 21 | TCP | ftp | File Transfer Protocol (FTP) port; sometimes used by File Service Protocol (FSP) |
| 22 | TCP | ssh | Secure Shell (SSH) service |
| 23 | TCP | telnet | The Telnet service |
| 25 | TCP | smtp | Simple Mail Transfer Protocol (SMTP) |
| 37 | TCP | time | Time Protocol |
| 39 | TCP | rlp | Resource Location Protocol |
| 42 | TCP | nameserver | Internet Name Service |
| 43 | TCP | nicname | WHOIS directory service |
| 49 | TCP | tacacs | Terminal Access Controller Access Control System for TCP/IP based authentication and access |
| 50 | TCP | re-mail-ck | Remote Mail Checking Protocol |
| 53 | TCP | domain | domain name services (such as BIND) |
| 63 | TCP | whois++ | WHOIS++, extended WHOIS services |
| 67 | TCP | bootps | Bootstrap Protocol (BOOTP) services; also used by Dynamic Host Configuration Protocol (DHCP) services |
| 68 | TCP | bootpc | Bootstrap (BOOTP) client; also used by Dynamic Host Control Protocol (DHCP) clients |
| 69 | TCP | tftp | Trivial File Transfer Protocol (TFTP) |
| 70 | TCP | gopher | Gopher Internet document search and retrieval |
| 71 | TCP | netrjs-1 | Remote Job Service |
| 72 | TCP | netrjs-2 | Remote Job Service |
| 73 | TCP | netrjs-3 | Remote Job Service |
| 73 | TCP | netrjs-4 | Remote Job Service |
| 79 | TCP | finger | Finger service for user contact information |
| 80 | TCP | http | HyperText Transfer Protocol (HTTP) for World Wide Web (WWW) services |
| 88 | TCP | kerberos | Kerberos network authentication system |
| 95 | TCP | supdup | Telnet protocol extension |
| 101 | TCP | hostname | Hostname services on SRI-NIC machines |
| 102 | TCP | iso-tsap | ISO Development Environment (ISODE) network applications |
| 105 | TCP | csnet-ns | Mailbox nameserver; also used by CSO nameserver |
| 107 | TCP | rtelnet | Remote Telnet |
| 109 | TCP | pop2 | Post Office Protocol version 2 |
| 110 | TCP | POP3 | Post Office Protocol version 3 |
| 111 | TCP | sunrpc | Remote Procedure Call (RPC) Protocol for remote command execution, used by Network Filesystem (NFS) |
| 113 | TCP | auth | Authentication and Ident protocols |
| 115 | TCP | sftp | Secure File Transfer Protocol (SFTP) services |
| 117 | TCP | uucp-path | Unix-to-Unix Copy Protocol (UUCP) Path services |
| 119 | TCP | nntp | Network News Transfer Protocol (NNTP) for the USENET discussion system |
| 123 | TCP | ntp | Network Time Protocol (NTP) |
| 137 | TCP | netbios-ns | NETBIOS Name Service used in Red Hat Enterprise Linux by Samba |
| 138 | TCP | netbios-dgm | NETBIOS Datagram Service used in Red Hat Enterprise Linux by Samba |
| 139 | TCP | netbios-ssn | NETBIOS Session Service used in Red Hat Enterprise Linux by Samba |
| 143 | TCP | IMAP | Internet Message Access Protocol (IMAP) |
| 161 | TCP | snmp | Simple Network Management Protocol (SNMP) |
| 162 | TCP | snmptrap | Traps for SNMP |
| 163 | TCP | cmip-man | Common Management Information Protocol (CMIP) |
| 164 | TCP | cmip-agent | Common Management Information Protocol (CMIP) |
| 174 | TCP | mailq | MAILQ email transport queue |
| 177 | TCP | xdmcp | X Display Manager Control Protocol (XDMCP) |
| 178 | TCP | nextstep | NeXTStep window server |
| 179 | TCP | bgp | Border Gateway Protocol |
| 191 | TCP | prospero | Prospero distributed filesystem services |
| 194 | TCP | irc | Internet Relay Chat (IRC) |
| 199 | TCP | smux | SNMP UNIX Multiplexer |
| 201 | TCP | at-rtmp | AppleTalk routing |
| 202 | TCP | at-nbp | AppleTalk name binding |
| 204 | TCP | at-echo | AppleTalk echo |
| 206 | TCP | at-zis | AppleTalk zone information |
| 209 | TCP | qmtp | Quick Mail Transfer Protocol (QMTP) |
| 210 | TCP | z39.50 | NISO Z39.50 database |
| 213 | TCP | ipx | Internetwork Packet Exchange (IPX), a datagram protocol commonly used in Novell Netware environments |
| 220 | TCP | IMAP3 | Internet Message Access Protocol version 3 |
| 245 | TCP | link | LINK / 3-DNS iQuery service |
| 347 | TCP | fatserv | FATMEN file and tape management server |
| 363 | TCP | rsvp_tunnel | RSVP Tunnel |
| 369 | TCP | rpc2portmap | Coda file system portmapper |
| 370 | TCP | codaauth2 | Coda file system authentication services |
| 372 | TCP | ulistproc | UNIX LISTSERV |
| 389 | TCP | ldap | Lightweight Directory Access Protocol (LDAP) |
| 427 | TCP | svrloc | Service Location Protocol (SLP) |
| 434 | TCP | mobileip-agent | Mobile Internet Protocol (IP) agent |
| 435 | TCP | mobilip-mn | Mobile Internet Protocol (IP) manager |
| 443 | TCP | https | Secure Hypertext Transfer Protocol (HTTP) |
| 444 | TCP | snpp | Simple Network Paging Protocol |
| 445 | TCP | microsoft-ds | Server Message Block (SMB) over TCP/IP |
| 464 | TCP | kpasswd | Kerberos password and key changing services |
| 468 | TCP | photuris | Photuris session key management protocol |
| 487 | TCP | saft | Simple Asynchronous File Transfer (SAFT) protocol |
| 488 | TCP | gss-http | Generic Security Services (GSS) for HTTP |
| 496 | TCP | pim-rp-disc | Rendezvous Point Discovery (RP-DISC) for Protocol Independent Multicast (PIM) services |
| 500 | TCP | isakmp | Internet Security Association and Key Management Protocol (ISAKMP) |
| 535 | TCP | iiop | Internet Inter-Orb Protocol (IIOP) |
| 538 | TCP | gdomap | GNUstep Distributed Objects Mapper (GDOMAP) |
| 546 | TCP | dhcpv6-client | Dynamic Host Configuration Protocol (DHCP) version 6 client |
| 547 | TCP | dhcpv6-server | Dynamic Host Configuration Protocol (DHCP) version 6 Service |
| 554 | TCP | rtsp | Real Time Stream Control Protocol (RTSP) |
| 563 | TCP | nntps | Network News Transport Protocol over Secure Sockets Layer (NNTPS) |
| 565 | TCP | whoami | whoami user ID listing |
| 587 | TCP | submission | Mail Message Submission Agent (MSA) |
| 610 | TCP | npmp-local | Network Peripheral Management Protocol (NPMP) local / Distributed Queueing System (DQS) |
| 611 | TCP | npmp-gui | Network Peripheral Management Protocol (NPMP) GUI / Distributed Queueing System (DQS) |
| 612 | TCP | hmmp-ind | HyperMedia Management Protocol (HMMP) Indication / DQS |
| 631 | TCP | ipp | Internet Printing Protocol (IPP) |
| 636 | TCP | ldaps | Lightweight Directory Access Protocol over Secure Sockets Layer (LDAPS) |
| 674 | TCP | acap | Application Configuration Access Protocol (ACAP) |
| 694 | TCP | ha-cluster | Heartbeat services for High-Availability Clusters |
| 749 | TCP | kerberos-adm | Kerberos version 5 (v5) ‘kadmin’ database administration |
| 750 | TCP | kerberos-iv | Kerberos version 4 (v4) services |
| 765 | TCP | webster | Network Dictionary |
| 767 | TCP | phonebook | Network Phonebook |
| 873 | TCP | rsync | rsync file transfer services |
| 992 | TCP | telnets | Telnet over Secure Sockets Layer (TelnetS) |
| 993 | TCP | IMAPS | Internet Message Access Protocol over Secure Sockets Layer (IMAPS) |
| 994 | TCP | ircs | Internet Relay Chat over Secure Sockets Layer (IRCS) |
| 995 | TCP | POP3s | Post Office Protocol version 3 over Secure Sockets Layer (POP3S) |
