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NAMEudp —
Internet User Datagram Protocol
SYNOPSIS#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int
DESCRIPTIONUDP is a simple, unreliable datagram protocol which is used to support theSOCK_DGRAM abstraction for the Internet protocol
family. UDP sockets are connectionless, and are normally used with the
sendto(2)
and
recvfrom(2)
calls, though the
connect(2)
call may also be used to fix the destination for future packets (in which case
the recv(2)
or read(2)
and send(2)
or
write(2)
system calls may be used).
UDP address formats are identical to those used by TCP. In particular UDP provides a port identifier in addition to the normal Internet address format. Note that the UDP port space is separate from the TCP port space (i.e., a UDP port may not be “connected” to a TCP port). In addition broadcast packets may be sent (assuming the underlying network supports this) by using a reserved “broadcast address”; this address is network interface dependent. Options at the IP transport level may be used with UDP; see
ip(4).
UDP_ENCAP socket option may be used at the IPPROTO_UDP level to encapsulate
ESP packets in UDP. Only one value is supported for this option:
UDP_ENCAP_ESPINUDP from RFC 3948, defined in
MIB VARIABLESTheudp protocol implements a number of variables in the
net.inet branch of the
sysctl(3)
MIB.
ERRORSA socket operation may fail with one of the following errors returned:
SEE ALSOgetsockopt(2), recv(2), send(2), socket(2), blackhole(4), inet(4), intro(4), ip(4), udplite(4)HISTORYTheudp protocol appeared in
4.2BSD.
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