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32 .\" @(#)udp.4 8.1 (Berkeley) 6/5/93
40 .Nd Internet User Datagram Protocol
46 .Fn socket AF_INET SOCK_DGRAM 0
49 is a simple, unreliable datagram protocol which is used
52 abstraction for the Internet
55 sockets are connectionless, and are
56 normally used with the
62 call may also be used to fix the destination for future
63 packets (in which case the
71 system calls may be used).
74 address formats are identical to those used by
78 provides a port identifier in addition
79 to the normal Internet address format.
83 space is separate from the
94 packets may be sent (assuming the underlying network supports
95 this) by using a reserved
96 .Dq broadcast address ;
98 is network interface dependent.
102 transport level may be used with
109 protocol implements a number of variables in the
114 .Bl -tag -width UDPCTL_RECVSPACEX
117 Enable udp checksums (enabled by default).
120 Maximum outgoing UDP datagram size
123 Maximum space for incoming UDP datagrams
125 For all udp datagrams, to ports on which there is no socket
126 listening, log the connection attempt (disabled by default).
128 When a datagram is received on a port where there is no socket
129 listening, do not return an ICMP port unreachable message.
130 (Disabled by default.
135 A socket operation may fail with one of the following errors returned:
138 when trying to establish a connection on a socket which
139 already has one, or when trying to send a datagram with the destination
140 address specified and the socket is already connected;
142 when trying to send a datagram, but
143 no destination address is specified, and the socket has not been
146 when the system runs out of memory for
147 an internal data structure;
150 is made to create a socket with a port which has already been
152 .It Bq Er EADDRNOTAVAIL
153 when an attempt is made to create a
154 socket with a network address for which no network interface