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UDP(4)		       FreeBSD Kernel Interfaces Manual			UDP(4)

NAME
     udp -- Internet User Datagram Protocol

SYNOPSIS
     #include <sys/socket.h>
     #include <netinet/in.h>

     int
     socket(AF_INET, SOCK_DGRAM, 0);

     int
     socket(AF_INET6, SOCK_DGRAM, 0);

DESCRIPTION
     UDP is a simple, unreliable datagram protocol which is used to support
     the SOCK_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) or
     ip6(4).

DIAGNOSTICS
     A socket operation	may fail with one of the following errors returned:

     [EISCONN]	      when trying to establish a connection on a socket	which
		      already has one, or when trying to send a	datagram with
		      the destination address specified	and the	socket is al-
		      ready connected;

     [ENOTCONN]	      when trying to send a datagram, but no destination ad-
		      dress is specified, and the socket hasn't	been con-
		      nected;

     [ENOBUFS]	      when the system runs out of memory for an	internal data
		      structure;

     [EADDRINUSE]     when an attempt is made to create	a socket with a	port
		      which has	already	been allocated;

     [EADDRNOTAVAIL]  when an attempt is made to create	a socket with a	net-
		      work address for which no	network	interface exists.

SEE ALSO
     getsockopt(2), recv(2), send(2), socket(2), inet(4), inet6(4), ip(4),
     ip6(4), netintro(4)

HISTORY
     The udp protocol appeared in 4.2BSD.

FreeBSD	13.0		      September	10, 2015		  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | HISTORY

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