文档介绍：RFC 768 J. Postel
ISI
28 August 1980
User Datagram Protocol
----------------------
Introduction
------------
This User Datagram Protocol (UDP) is defined to make available a
datagram mode of packet-munication in the
environment of an interconnected set works. This
protocol assumes that the Protocol (IP) [1] is used as the
underlying protocol.
This protocol provides a procedure for application programs to send
messages to other programs with a minimum of protocol mechanism. The
protocol is transaction oriented, and delivery and duplicate protection
are not guaranteed. Applications requiring ordered reliable delivery of
streams of data should use the Transmission Control Protocol (TCP) [2].
Format
------
0 7 8 15 16 23 24 31
+--------+--------+--------+--------+
| Source | Destination |
| Port | Port |
+--------+--------+--------+--------+
| | |
| Length | Checksum |
+--------+--------+--------+--------+
|
| data octets ...
+---------------- ...
User Datagram Header Format
Fields
------
Source Port is an optional field, when meaningful, it indicates the port
of the sending process, and may be assumed to be the port to which a
reply should be addressed in the absence of any other information. If
not used, a value of zero is inserted.
Postel [page 1]
28 Aug 1980
User Datagram Protocol RFC 768
Fields
Destination P