592:
as RFC 433 in
December 1972 and included a list of hosts and their port numbers and the corresponding function used at each host in the network. This first registry function served primarily as documentation of usage and indicated that port number usage was conflicting between some hosts for "useful public services". The document promised a resolution of the conflicts based on a standard that Postel had published in May 1972 in RFC 349, in which he first proposed official assignments of port numbers to network services and suggested a dedicated administrative function, which he called a
88:, and the type of transport protocol used for communication. It completes the destination or origination address of a message. Specific port numbers are reserved to identify specific services so that an arriving packet can be easily forwarded to a running application. For this purpose, port numbers lower than 1024 identify the historically most commonly used services and are called the
176:(IANA). In many operating systems special privileges are required for applications to bind to these ports because these are often deemed critical to the operation of IP networks. Conversely, the client end of a connection typically uses a high port number allocated for short-term use, therefore called an
591:
called for documenting the then-current usages and establishing a socket number catalog in RFC 322. Network administrators were asked to submit a note or place a phone call, "describing the function and socket numbers of network service programs at each HOST". This catalog was subsequently published
524:
While the listening port number of a server is well defined (IANA calls these the well-known ports), the client's port number is often chosen from the dynamic port range (see below). In some applications, the clients and the server each use specific port numbers assigned by the IANA. A good example
569:
in the early development stages of the network. A socket number for a remote host was a 40-bit quantity. The first 32 bits were similar to today's IPv4 address, but at the time the most-significant 8 bits were the host number. The least-significant portion of the socket number (bits 33 through 40)
520:
applications on users' personal computers to fetch email messages from the server. The POP service listens on TCP port number 110. Both services may be running on the same host computer, in which case the port number distinguishes the service that was requested by a remote computer, be it a user's
168:, and involves the receipt of a request on the well-known port potentially establishing a one-to-one server-client dialog, using this listening port. Other clients may simultaneously connect to the same listening port; this works because a TCP connection is identified by a
148:. A socket is used by a process to send and receive data via the network. The operating system's networking software has the task of transmitting outgoing data from all application ports onto the network, and forwarding arriving
194:
IANA is responsible for the global coordination of the DNS root, IP addressing, and other protocol resources. This includes the registration of commonly used TCP and UDP port numbers for well-known internet services.
115:
For TCP and UDP, a port number is a 16-bit unsigned integer, thus ranging from 0 to 65535. For TCP, port number 0 is reserved and cannot be used, while for UDP, the source port is optional and a value of zero means
152:
to processes by matching the packet's IP address and port number to a socket. For TCP, only one process may bind to a specific IP address and port combination. Common application failures, sometimes called
488:
attempts or with network administrators looking for possible vulnerabilities to help prevent such attacks. Port connection attempts are frequently monitored and logged by hosts. The technique of
504:. A server used for sending and receiving email generally needs two services. The first service is used to transport email to and from other servers. This is accomplished with the
464:, and they can be readily interpreted not only by the sending and receiving hosts but also by other components of the networking infrastructure. In particular,
172:
consisting of the local address, the local port, the remote address, and the remote port. The well-known ports are defined by convention overseen by the
727:
is still closely connected with port numbers, the former being text strings used in some network functions to represent a numerical port number.
45:
is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an
788:
Internet
Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry
221:) are those numbered from 0 through 1023. The requirements for new assignments in this range are stricter than for other registrations.
508:(SMTP). A standard SMTP service application listens on TCP port 25 for incoming requests. The second service is usually either the
449:
823:
418:
The registered ports are those from 1024 through 49151. IANA maintains the official list of well-known and registered ranges.
61:
and address combination by the port number assigned to it. The most common transport protocols that use port numbers are the
307:
173:
720:
376:
460:
field for indicating the source and destination port numbers. The port numbers are encoded in the transport protocol
513:
365:
189:
157:, occur when multiple programs attempt to use the same port number on the same IP address with the same protocol.
792:
107:
of application architecture, multiple simultaneous communication sessions may be initiated for the same service.
580:
refers to a related but distinct concept, namely the internal address of an endpoint used only within the node.
343:
505:
437:
285:
62:
650:
service received the first official assignment of the value 1. In detail, the first set of assignments was:
480:
The practice of attempting to connect to a range of ports in sequence on a single host is commonly known as
468:
are commonly configured to differentiate between packets based on their source or destination port numbers.
1051:
1046:
318:
421:
The dynamic or private ports are those from 49152 through 65535. One common use for this range is for
538:
433:
20:
492:
uses a series of port connections (knocks) from a client computer to enable a server connection.
161:
104:
89:
103:
service for multiple services or multiple communication sessions at one network address. In the
441:
252:
241:
66:
465:
354:
27:
596:, to maintain a registry. The 256 values of the AEN were divided into the following ranges:
996:
962:
925:
891:
854:
806:
761:
509:
332:
8:
387:
121:
50:
457:
445:
296:
133:
92:. Higher-numbered ports are available for general use by applications and are known as
58:
723:(NCP). NCP was the forerunner of the modern Internet protocols. Today the terminology
485:
529:
in which the client always uses UDP port 68 and the server always uses UDP port 67.
986:
952:
915:
881:
844:
796:
751:
655:
46:
34:
469:
137:
129:
125:
77:
70:
54:
809:
786:
561:
in informal cooperation of software authors and system administrators. The term
999:
980:
965:
946:
928:
909:
894:
875:
784:
764:
745:
659:
576:
422:
322:
177:
149:
93:
81:
857:
838:
719:, and was used with the Initial Connection Protocol (ICP), a component of the
541:(URLs). By default, HTTP uses port 80 and HTTPS uses port 443, but a URL like
1040:
489:
481:
461:
19:
This article is about software communication ports. For physical ports, see
557:
The concept of port numbers was established by the early developers of the
517:
263:
100:
160:
Applications implementing common services often use specifically reserved
546:
398:
588:
141:
85:
26:"port (network)" redirects here. For ports in electrical networks, see
164:
for receiving service requests from clients. This process is known as
991:
957:
920:
886:
849:
801:
756:
584:
453:
558:
647:
409:
274:
501:
169:
565:
was not yet in use. It was preceded by the use of the term
526:
49:, a port is a logical construct that identifies a specific
785:
Michelle Cotton; Lars Eggert; et al. (August 2011).
57:. A port at the software level is identified for each
198:
The port numbers are divided into three ranges: the
484:. This is usually associated either with malicious
549:connects instead to port 8080 of the HTTP server.
500:An example of the use of ports is the delivery of
1024:
1038:
715:In the early ARPANET, the AEN was also called a
537:Port numbers are sometimes seen in web or other
277:remote login service, unencrypted text messages
978:
124:associates its input or output channels via an
16:Communications endpoint in an operating system
1029:. Menlo Park, CA: Network Information Center.
826:. Internet Assigned Numbers Authority (IANA).
873:
874:Postel, J.; Neigus, N. (22 December 1972).
979:Shoshani, A.; Harslem, E. (14 July 1971).
907:
76:A port number is always associated with a
990:
956:
919:
885:
848:
800:
755:
940:
938:
869:
867:
836:
1039:
944:
908:Cerf, V.; Postel, J. (26 March 1972).
183:
144:, and a port number. This is known as
982:Initial Connection Protocol--Reviewed
935:
864:
69:(UDP); those port numbers are 16-bit
830:
217:The well-known ports (also known as
816:
472:is an example application of this.
428:
308:Dynamic Host Configuration Protocol
174:Internet Assigned Numbers Authority
13:
743:
377:Simple Network Management Protocol
368:(IMAP) Management of digital mail
14:
1063:
1025:Postel, Jon; Feinler, E. (1978).
1006:
543:http://www.example.com:8080/path/
521:computer or another mail server.
948:Proposed Standard Socket Numbers
616:Network-wide standard functions
514:Internet Message Access Protocol
475:
366:Internet Message Access Protocol
225:Notable well-known port numbers
190:List of TCP and UDP port numbers
1018:
972:
901:
778:
737:
532:
448:(PDUs). For TCP, the PDU is a
344:Network News Transfer Protocol
110:
1:
837:Crocker, S. (16 March 1970).
730:
506:Simple Mail Transfer Protocol
438:Transmission Control Protocol
286:Simple Mail Transfer Protocol
63:Transmission Control Protocol
7:
495:
444:(UDP), transfer data using
319:Hypertext Transfer Protocol
10:
1068:
945:Postel, J. (30 May 1972).
747:Transport Control Protocol
640:Any experimental function
574:, abbreviated AEN. Today,
552:
401:(HTTPS) HTTP over TLS/SSL
187:
25:
18:
1027:ARPANET Protocol Handbook
1014:ARPANET Protocol Handbook
911:Well Known Socket Numbers
705:
697:
689:
681:
673:
668:
665:
636:
628:
620:
612:
607:
604:
539:uniform resource locators
434:Transport-layer protocols
405:
394:
383:
372:
361:
350:
339:
328:
314:
303:
292:
281:
270:
259:
248:
237:
232:
229:
721:Network Control Protocol
632:Reserved for future use
624:Host-specific functions
516:(IMAP) which is used by
21:Computer port (hardware)
572:Another Eightbit Number
456:. Both protocols use a
162:well-known port numbers
90:well-known port numbers
452:, and for UDP it is a
442:User Datagram Protocol
288:(SMTP) email delivery
255:(FTP) Command Control
253:File Transfer Protocol
242:File Transfer Protocol
67:User Datagram Protocol
570:was an entity called
412:IPv6 version of DHCP
355:Network Time Protocol
128:, which is a type of
28:Port (circuit theory)
654:Port assignments in
510:Post Office Protocol
333:Post Office Protocol
244:(FTP) Data Transfer
132:, associated with a
662:
601:
583:On March 26, 1972,
545:specifies that the
446:protocol data units
388:Internet Relay Chat
321:(HTTP) used in the
266:(SSH) Secure Login
226:
184:Common port numbers
105:client–server model
35:computer networking
1052:1972 introductions
1047:Internet protocols
877:Socket number list
653:
605:Port number range
599:
297:Domain Name System
224:
134:transport protocol
59:transport protocol
713:
712:
693:Remote job entry
644:
643:
416:
415:
1059:
1031:
1030:
1022:
1016:
1010:
1004:
1003:
994:
992:10.17487/RFC0197
976:
970:
969:
960:
958:10.17487/RFC0349
942:
933:
932:
923:
921:10.17487/RFC0322
905:
899:
898:
889:
887:10.17487/RFC0433
871:
862:
861:
852:
850:10.17487/RFC0036
834:
828:
827:
820:
814:
813:
804:
802:10.17487/RFC6335
782:
776:
775:
773:
771:
759:
757:10.17487/RFC0793
741:
663:
652:
637:240 through 255
629:128 through 239
602:
598:
544:
429:Network behavior
227:
223:
204:registered ports
200:well-known ports
99:Ports provide a
71:unsigned numbers
47:operating system
1067:
1066:
1062:
1061:
1060:
1058:
1057:
1056:
1037:
1036:
1035:
1034:
1023:
1019:
1011:
1007:
977:
973:
943:
936:
906:
902:
872:
865:
835:
831:
822:
821:
817:
805:. BCP 165.
783:
779:
769:
767:
742:
738:
733:
621:64 through 127
555:
542:
535:
498:
478:
470:Port forwarding
431:
423:ephemeral ports
192:
186:
150:network packets
138:network address
130:file descriptor
126:internet socket
113:
94:ephemeral ports
78:network address
55:network service
31:
24:
17:
12:
11:
5:
1065:
1055:
1054:
1049:
1033:
1032:
1017:
1005:
971:
934:
900:
863:
840:Protocol Notes
829:
824:"Port Numbers"
815:
777:
744:Postel, John.
735:
734:
732:
729:
711:
710:
707:
703:
702:
699:
695:
694:
691:
687:
686:
685:File transfer
683:
679:
678:
675:
671:
670:
667:
642:
641:
638:
634:
633:
630:
626:
625:
622:
618:
617:
614:
610:
609:
606:
577:network socket
554:
551:
534:
531:
497:
494:
477:
474:
440:(TCP) and the
436:, such as the
430:
427:
414:
413:
407:
403:
402:
396:
392:
391:
385:
381:
380:
374:
370:
369:
363:
359:
358:
352:
348:
347:
341:
337:
336:
330:
326:
325:
323:World Wide Web
316:
312:
311:
305:
301:
300:
299:(DNS) service
294:
290:
289:
283:
279:
278:
272:
268:
267:
261:
257:
256:
250:
246:
245:
239:
235:
234:
231:
188:Main article:
185:
182:
178:ephemeral port
155:port conflicts
112:
109:
65:(TCP) and the
15:
9:
6:
4:
3:
2:
1064:
1053:
1050:
1048:
1045:
1044:
1042:
1028:
1021:
1015:
1009:
1001:
998:
993:
988:
984:
983:
975:
967:
964:
959:
954:
950:
949:
941:
939:
930:
927:
922:
917:
913:
912:
904:
896:
893:
888:
883:
879:
878:
870:
868:
859:
856:
851:
846:
842:
841:
833:
825:
819:
811:
808:
803:
798:
794:
790:
789:
781:
766:
763:
758:
753:
749:
748:
740:
736:
728:
726:
722:
718:
708:
704:
700:
696:
692:
688:
684:
680:
676:
672:
664:
661:
657:
651:
649:
639:
635:
631:
627:
623:
619:
615:
613:0 through 63
611:
603:
597:
595:
590:
586:
581:
579:
578:
573:
568:
567:socket number
564:
560:
550:
548:
540:
530:
528:
522:
519:
515:
512:(POP) or the
511:
507:
503:
493:
491:
490:port knocking
487:
483:
482:port scanning
476:Port scanning
473:
471:
467:
463:
462:packet header
459:
455:
451:
447:
443:
439:
435:
426:
424:
419:
411:
408:
404:
400:
397:
393:
389:
386:
382:
378:
375:
371:
367:
364:
360:
356:
353:
349:
345:
342:
338:
334:
331:
327:
324:
320:
317:
313:
309:
306:
302:
298:
295:
291:
287:
284:
280:
276:
273:
269:
265:
262:
258:
254:
251:
247:
243:
240:
236:
228:
222:
220:
215:
213:
212:private ports
209:
205:
201:
196:
191:
181:
179:
175:
171:
167:
163:
158:
156:
151:
147:
143:
139:
135:
131:
127:
123:
119:
108:
106:
102:
97:
95:
91:
87:
84:, such as an
83:
79:
74:
72:
68:
64:
60:
56:
53:or a type of
52:
48:
44:
40:
36:
29:
22:
1026:
1020:
1013:
1008:
981:
974:
947:
910:
903:
876:
839:
832:
818:
787:
780:
768:. Retrieved
746:
739:
725:service name
724:
716:
714:
666:Port number
645:
593:
582:
575:
571:
566:
562:
556:
536:
523:
518:email client
499:
479:
432:
420:
417:
264:Secure Shell
219:system ports
218:
216:
211:
207:
203:
199:
197:
193:
165:
159:
154:
145:
117:
114:
101:multiplexing
98:
75:
42:
38:
32:
717:socket name
669:Assignment
608:Assignment
600:AEN ranges
563:port number
547:web browser
533:Use in URLs
525:of this is
399:HTTP Secure
233:Assignment
140:such as an
111:Port number
43:port number
1041:Categories
1012:NIC 7104,
731:References
589:Jon Postel
206:, and the
142:IP address
86:IP address
770:1 January
585:Vint Cerf
466:firewalls
406:546, 547
166:listening
709:Discard
496:Examples
486:cracking
454:datagram
677:Telnet
559:ARPANET
553:History
450:segment
379:(SNMP)
346:(NNTP)
335:(POP3)
310:(DHCP)
304:67, 68
230:Number
208:dynamic
146:binding
122:process
118:no port
51:process
658:
648:Telnet
458:header
410:DHCPv6
390:(IRC)
357:(NTP)
275:Telnet
202:, the
701:Echo
502:email
170:tuple
80:of a
810:6335
793:IETF
772:2023
646:The
594:czar
587:and
527:DHCP
395:443
384:194
373:161
362:143
351:123
340:119
329:110
136:, a
120:. A
82:host
39:port
37:, a
1000:197
997:RFC
987:doi
966:349
963:RFC
953:doi
929:322
926:RFC
916:doi
895:433
892:RFC
882:doi
855:RFC
845:doi
807:RFC
797:doi
765:793
762:RFC
752:doi
660:349
656:RFC
315:80
293:53
282:25
271:23
260:22
249:21
238:20
210:or
41:or
33:In
1043::
995:.
985:.
961:.
951:.
937:^
924:.
914:.
890:.
880:.
866:^
858:36
853:.
843:.
795:.
791:.
760:.
750:.
706:9
698:7
690:5
682:3
674:1
425:.
214:.
180:.
96:.
73:.
1002:.
989::
968:.
955::
931:.
918::
897:.
884::
860:.
847::
812:.
799::
774:.
754::
30:.
23:.
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