206 lines
5.2 KiB
Groff
206 lines
5.2 KiB
Groff
.\" $NetBSD: udp.4,v 1.12 2011/09/24 18:49:13 christos Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)udp.4 8.1 (Berkeley) 6/5/93
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.\"
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.Dd September 24, 2011
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.Dt UDP 4
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.Os
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.Sh NAME
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.Nm udp
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.Nd Internet User Datagram Protocol
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.Sh SYNOPSIS
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.In sys/socket.h
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.In netinet/in.h
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.Ft int
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.Fn socket AF_INET SOCK_DGRAM 0
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.Ft int
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.Fn socket AF_INET6 SOCK_DGRAM 0
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.Sh DESCRIPTION
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.Tn UDP
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is a simple, unreliable datagram protocol which is used
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to support the
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.Dv SOCK_DGRAM
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abstraction for the Internet
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protocol family.
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.Tn UDP
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sockets are connectionless, and are
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normally used with the
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.Xr sendto 2
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and
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.Xr recvfrom 2
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calls, though the
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.Xr connect 2
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call may also be used to fix the destination for future
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packets (in which case the
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.Xr recv 2
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or
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.Xr read 2
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and
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.Xr send 2
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or
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.Xr write 2
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system calls may be used).
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.Pp
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.Tn UDP
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address formats are identical to those used by
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.Tn TCP .
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In particular
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.Tn UDP
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provides a port identifier in addition
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to the normal Internet address format.
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Note that the
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.Tn UDP
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port
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space is separate from the
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.Tn TCP
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port space (i.e. a
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.Tn UDP
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port
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may not be
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.Dq connected
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to a
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.Tn TCP
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port).
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In addition broadcast packets may be sent (assuming the underlying
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network supports this) by using a reserved
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.Dq broadcast address ;
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this address
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is network interface dependent.
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.Pp
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There are two
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.Tn UDP-level
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.Xr setsockopt 2 Ns / Ns Xr getsockopt 2
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options.
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.Dv UDP_OPTIONS
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may be used to change the default behavior of the socket.
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For example:
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.Bd -literal
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setsockopt(s, IPPROTO_UDP, UDP_OPTIONS, NULL, 0);
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.Ed
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.Pp
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The
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.Dv UDP_ENCAP
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option can be used to encapsulate
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.Tn ESP
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packets in
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.Tn UDP .
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There are two valid enapsulation options:
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.Tn UDP_ENCAP_ESPINUDP_NON_IKE
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from draft-ietf-ipsec-nat-t-ike-00/01 and
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.Tn UDP_ENCAP_ESPINUDP
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from draft-ietf-ipsec-udp-encaps-06
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defined in
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.In netinet/udp.h .
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.Pp
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The
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.Dv UDP_RFC6056ALGO
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can be used to randomize the port selection.
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Valid algorithms are described in
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.Xr rfc6056 7
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and their respective constants are in
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.In netinet/rfc6056.h .
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For example,
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.Bd -literal
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int algo = RFC6056_ALGO_RANDOM_PICK; /* see \*[Lt]netinet/rfc6056.h\*[Gt] */
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setsockopt(s, IPPROTO_UDP, UDP_RFC6056ALGO, \*[Am]algo, sizeof(algo));
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.Ed
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.Pp
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The port selection can be also controlled at a global level for all
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.Tn UDP
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or
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.Tn UDP6
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sockets using the following
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.Xr sysctl 7
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variables:
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.Dv net.inet.udp.rfc6056.selected
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and
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.Dv net.inet6.udp6.rfc6056.selected
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respectively.
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.Pp
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Options at the
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.Tn IP
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transport level may be used with
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.Tn UDP ;
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see
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.Xr ip 4
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or
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.Xr ip6 4 .
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.Sh DIAGNOSTICS
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A socket operation may fail with one of the following errors returned:
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.Bl -tag -width [EADDRNOTAVAIL]
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.It Bq Er EISCONN
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when trying to establish a connection on a socket which
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already has one, or when trying to send a datagram with the destination
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address specified and the socket is already connected;
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.It Bq Er ENOTCONN
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when trying to send a datagram, but
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no destination address is specified, and the socket hasn't been
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connected;
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.It Bq Er ENOBUFS
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when the system runs out of memory for
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an internal data structure;
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.It Bq Er EADDRINUSE
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when an attempt
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is made to create a socket with a port which has already been
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allocated;
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.It Bq Er EADDRNOTAVAIL
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when an attempt is made to create a socket with a network address
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for which no network interface exists.
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.El
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.Sh SEE ALSO
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.Xr getsockopt 2 ,
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.Xr recv 2 ,
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.Xr send 2 ,
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.Xr socket 2 ,
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.Xr inet 4 ,
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.Xr inet6 4 ,
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.Xr intro 4 ,
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.Xr ip 4 ,
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.Xr ip6 4 ,
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.Xr rfc6056 7 ,
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.Xr sysctl 7
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.Rs
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.%R RFC
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.%N 768
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.%D August 28, 1980
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.%T "User Datagram Protocol"
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.Re
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.Rs
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.%R RFC
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.%N 1122
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.%D October 1989
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.%T "Requirements for Internet Hosts -- Communication Layers"
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.Re
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.Sh HISTORY
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The
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.Nm
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protocol appeared in
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.Bx 4.2 .
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