TCP 和 UDP 都是 IP 层的传输协议，是 IP 与上层之间的处理接口。TCP 和 UDP 协议端口号被设计来区分运行在单个设备上的多重应用程序的 IP 地址。
由于同一台机器上可能会运行多个网络应用程序，所以计算机需要确保目标计算机上接收源主机数据包的软件应用程序的正确性，以及响应能够被发送到源主机的正确应用程序上。该过程正是通过使用TCP 或 UDP 端口号来实现的。在 TCP 和 UDP 头部分，有“源端口”和“目标端口”段，主要用于显示发送和接收过程中的身份识别信息。IP 地址和端口号合在一起被称为“套接字”。
IETF IANA 定义了三种端口组：公认端口（Well Known Ports）、注册端口（RegisteredPorts）以及动态和/或私有端口（Dynamic and/or Private Ports） 。
公认端口（Well Known Ports）从0到1023。
注册端口（RegisteredPorts）从1024到49151。
动态和/或私有端口（Dynamic and/or Private Ports）从49152到65535。
部分TCP/UDP端口
端口号协议服务名称别名注释
7TCPecho Echo
7UDPecho Echo
9TCPdiscardsink nullDiscard
9UDPdiscardsink nullDiscard
13TCPdaytime Daytime
13UDPdaytime Daytime
17TCPqotdquoteQuote of the day
17UDPqotdquoteQuote of the day
19TCPchargenttytst sourceCharacter generator
19UDPchargenttytst sourceCharacter generator
20TCPftp-data File Transfer
21TCPftp FTP Control
23TCPtelnet Telnet
25TCPsmtpmailSimple Mail Transfer
37TCPtime Time
37UDPtime Time
39UDPrlpresourceResource Location Protocol
42TCPnameservernameHost Name Server
42UDPnameservernameHost Name Server
43TCPnicnamewhoisWho Is
53TCPdomain Domain Name
53UDPdomain Domain Name Server
67UDPbootpsdhcpsBootstrap Protocol Server
68UDPbootpcdhcpcBootstrap Protocol Client
69UDPtftp Trivial File Transfer
70TCPgopher Gopher
79TCPfinger Finger
80TCPhttpwww，httpWorld Wide Web
88TCPkerberoskrb5Kerberos
88UDPkerberoskrb5Kerberos
101TCPhostnamehostnamesNIC Host Name Server
102TCPiso-tsap ISO-TSAP Class 0
107TCPrtelnet Remote Telnet Service
109TCPpop2postofficePost Office Protocol - Version 2
110TCPpop3postofficePost Office Protocol - Version 3
111TCPsunrpcrpcbind portmapSUN Remote Procedure Call
111UDPsunrpcrpcbind portmapSUN Remote Procedure Call
113TCPauthident tapAuthentication Sevice
117TCPuucp-path UUCP Path Service
119TCPnntpusenetNetwork News Transfer Protocol
123UDPntp Network Time Protocol
135TCPepmaploc-srvDCE endpoint resolution
135UDPepmaploc-srvDCE endpoint resolution
137TCPnetbios-nsnbnameNETBIOS Name Service
137UDPnetbios-nsnbnameNETBIOS Name Service
138UDPnetbios-dgmnbdatagramNETBIOS Datagram Service
139TCPnetbios-ssnnbsessionNETBIOS Session Service
143TCPimapimap4Internet Message Access Protocol
158TCPpcmail-srvrepositoryPC Mail Server
161UDPsnmpsnmpSNMP
162UDPsnmptrapsnmp-trapSNMP TRAP
170TCPprint-srv Network PostScript
179TCPbgp Border Gateway Protocol
194TCPirc Internet Relay Chat Protocol
213UDPipx IPX over IP
389TCPldap Lightweight Directory Access Protocol
443TCPS-HTTPMCom
443UDPS-HTTPMCom
445TCP Microsoft CIFS
445UDP Microsoft CIFS
464TCPkpasswd Kerberos (v5)
464UDPkpasswd Kerberos (v5)
500UDPisakmpikeInternet Key Exchange (IPSec)
512TCPexec Remote Process Execution
512UDPbiffcomsatNotifies users of new mail
513TCPlogin Remote Login
513UDPwhowhodDatabase of who's logged on，average load
514TCPcmdshellAutomatic Authentication
514UDPsyslog
515TCPprinterspoolerListens for incoming connections
517UDPtalk Establishes TCP Connection
518UDPntalk
520TCPefs Extended File Name Server
520UDProuterrouter routedRIPv.1，RIPv.2
525UDPtimedtimeserverTimeserver
526TCPtemponewdateNewdate
530TCP,UDPcourierrpcRPC
531TCPconferencechatIRC Chat
532TCPnetnewsreadnewsReadnews
533UDPnetwall For emergency broadcasts
540TCPuucpuucpdUucpd
543TCPklogin Kerberos login
544TCPkshellkrcmdKerberos remote shell
550UDPnew-rwhonew-whoNew-who
556TCPremotefsrfs rfs_serverRfs Server
560UDPrmonitorrmonitordRmonitor
561UDPmonitor
636TCPldapssldapLDAP over TLS/SSL
749TCPkerberos-adm Kerberos administration
749UDPkerberos-adm Kerberos administration
