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udp(7) Miscellaneous Information Manual udp(7) NAME udp - Internet user datagram protocol (UDP) SYNOPSIS #include <sys/socket.h> #include <netinet/in.h> s = socket(AF_INET, SOCK_DGRAM, 0); DESCRIPTION UDP is a simple, unreliable datagram protocol that is used to support the SOCK_DGRAM abstraction for the Internet Protocol family. UDP sock- ets are connectionless, and are normally used with the sendto() and recvfrom() functions, though the connect() function may also be used to fix the destination for future packets, in which case the recv() or read() and send() or write() functions 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 ad- dress format. Note that the UDP port space is separate from the TCP port space (that is, 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 the ip() reference page. ERRORS If a socket operation fails, errno may be set to one of the following values: The socket is already connected. This error occurs when trying to establish connection on a socket or when trying to send a datagram with the destination address specified. The destination address of a datagram was not specified, and the socket has not been connected. The system ran out of memory for an internal data structure. An attempt was made to create a socket with a port that has already been allo- cated. An attempt was made to create a socket with a network address for which no network interface exists. RELATED INFORMATION Functions: getsockopt(2), recv(2), send(2), socket(2) Files: netintro(7), inet(7), ip(7) delim off udp(7)