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32 .\" @(#)udp.4 8.1 (Berkeley) 6/5/93
33 .\" $FreeBSD: src/share/man/man4/udp.4,v 1.8.2.4 2001/12/17 11:30:12 ru Exp $
34 .\" $DragonFly: src/share/man/man4/udp.4,v 1.2 2003/06/17 06:36:59 dillon Exp $
41 .Nd Internet User Datagram Protocol
47 .Fn socket AF_INET SOCK_DGRAM 0
50 is a simple, unreliable datagram protocol which is used
53 abstraction for the Internet
56 sockets are connectionless, and are
57 normally used with the
63 call may also be used to fix the destination for future
64 packets (in which case the
72 system calls may be used).
75 address formats are identical to those used by
79 provides a port identifier in addition
80 to the normal Internet address format. Note that the
83 space is separate from the
92 port). In addition broadcast
93 packets may be sent (assuming the underlying network supports
94 this) by using a reserved
95 .Dq broadcast address ;
97 is network interface dependent.
101 transport level may be used with
106 A socket operation may fail with one of the following errors returned:
109 when trying to establish a connection on a socket which
110 already has one, or when trying to send a datagram with the destination
111 address specified and the socket is already connected;
113 when trying to send a datagram, but
114 no destination address is specified, and the socket hasn't been
117 when the system runs out of memory for
118 an internal data structure;
121 is made to create a socket with a port which has already been
123 .It Bq Er EADDRNOTAVAIL
124 when an attempt is made to create a
125 socket with a network address for which no network interface
131 protocol implements a number of variables in the
136 .Bl -tag -width UDPCTL_RECVSPACEX
139 Enable udp checksums (enabled by default).
142 Maximum outgoing UDP datagram size
145 Maximum space for incoming UDP datagrams
147 For all udp datagrams, to ports on which there is no socket
148 listening, log the connection attempt (disabled by default).
150 When a datagram is received on a port where there is no socket
151 listening, do not return an ICMP port unreachable message.
152 (Disabled by default. See