Appendix B: Well-known Protocol, Port, and Other Numbers 285
Both UDP and TCP port numbers are divided into the following ranges:
■ Well-known port numbers (0 through 1023)
■ Registered port numbers (1024 through 49151)
■ Dynamic or private port numbers (49152 through 65535)
Usually, a port assignment uses a common port number for both UDP and TCP. A con-
nection from a client to a server uses the well-known port on the server as a service con-
tact port, whereas the client is free to dynamically assign its own port number. For TCP,
the connection is identified by the source and destination IP addresses, as well as the
source and destination TCP port numbers.
Well-known or assigned IP protocols are registered with the IANA. The information pre-
sented here is reproduced with permission from the IANA. For the most current
IP protocol number assignment information, refer to www.iana.org/numbers.htm
under the “Port Numbers” link.
Table B-3 shows some commonly used protocols, their port numbers, and a brief descrip-
tion. The IANA has recorded around 3350 unique port numbers. Because of space limita-
tions, only a small subset of these port numbers are presented here.
Table B-3 Commonly Used Protocols and Associated Port Numbers
Keyword Description UDP/TCP
Port
echo Echo 7
discard Discard 9
systat Active Users 11
daytime Daytime (RFC 867) 13
qotd Quote of the Day 17
chargen Character Generator 19
ftp-data File Transfer [Default Data] 20
ftp File Transfer [Control] 21
ssh SSH Remote Login Protocol 22
telnet Telnet 23
Any private mail system Any private mail system 24
smtp Simple Mail Transfer 25
msg-icp MSG ICP 29
msg-auth MSG Authentication 31
Any private printer server Any private printer server 35
Section B-3
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