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NetBSD 6.1.5 - man page for sendto (netbsd section 2)

SEND(2) 			     BSD System Calls Manual				  SEND(2)

NAME
     send, sendto, sendmsg -- send a message from a socket

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/socket.h>

     ssize_t
     send(int s, const void *msg, size_t len, int flags);

     ssize_t
     sendto(int s, const void *msg, size_t len, int flags, const struct sockaddr *to,
	 socklen_t tolen);

     ssize_t
     sendmsg(int s, const struct msghdr *msg, int flags);

DESCRIPTION
     send(), sendto(), and sendmsg() are used to transmit a message to another socket.	send()
     may be used only when the socket is in a connected state, while sendto() and sendmsg() may
     be used at any time.

     The address of the target is given by to with tolen specifying its size.  The length of the
     message is given by len.  If the message is too long to pass atomically through the underly-
     ing protocol, the error EMSGSIZE is returned, and the message is not transmitted.

     No indication of failure to deliver is implicit in a send().  Locally detected errors are
     indicated by a return value of -1.

     If no messages space is available at the socket to hold the message to be transmitted, then
     send() normally blocks, unless the socket has been placed in non-blocking I/O mode.  The
     select(2) or poll(2) call may be used to determine when it is possible to send more data.

     The flags parameter may include one or more of the following:

     #define MSG_OOB	     0x0001 /* process out-of-band data */
     #define MSG_PEEK	     0x0002 /* peek at incoming message */
     #define MSG_DONTROUTE   0x0004 /* bypass routing, use direct interface */
     #define MSG_EOR	     0x0008 /* data completes record */
     #define MSG_NOSIGNAL    0x0400 /* do not generate SIGPIPE on EOF */

     The flag MSG_OOB is used to send ``out-of-band'' data on sockets that support this notion
     (e.g.  SOCK_STREAM); the underlying protocol must also support ``out-of-band'' data.
     MSG_EOR is used to indicate a record mark for protocols which support the concept.
     MSG_DONTROUTE is usually used only by diagnostic or routing programs.

     See recv(2) for a description of the msghdr structure.  MSG_NOSIGNAL is used to prevent
     SIGPIPE generation when writing a socket that may be closed.

RETURN VALUES
     The call returns the number of characters sent, or -1 if an error occurred.

ERRORS
     send(), sendto(), and sendmsg() fail if:

     [EBADF]		An invalid descriptor was specified.

     [ENOTSOCK] 	The argument s is not a socket.

     [EFAULT]		An invalid user space address was specified for a parameter.

     [EMSGSIZE] 	The socket requires that message be sent atomically, and the size of the
			message to be sent made this impossible.

     [EPIPE]		In a connected socket the connection has been broken.

     [EDSTADDRREQ]	In a non-connected socket a destination address has not been specified.

     [EAGAIN|EWOULDBLOCK]
			The socket is marked non-blocking and the requested operation would
			block.

     [ENOBUFS]		The system was unable to allocate an internal buffer.  The operation may
			succeed when buffers become available.

     [ENOBUFS]		The output queue for a network interface was full.  This generally indi-
			cates that the interface has stopped sending, but may be caused by tran-
			sient congestion.

     [EACCES]		The SO_BROADCAST option is not set on the socket, and a broadcast address
			was given as the destination.

     [EHOSTUNREACH]	The destination for the message is unreachable.

     [EHOSTDOWN]	The destination is a host on the local subnet and does not respond to
			arp(4).

     [EINVAL]		The total length of the I/O is more than can be expressed by the ssize_t
			return value.

     [EAFNOSUPPORT]	Addresses in the specified address family cannot be used with this
			socket.

     sendto() will also fail if:

     [EISCONN]		A destination address was specified and the socket is already connected.

     sendmsg() will also fail if:

     [EMSGSIZE] 	The msg_iovlen member of the msg structure is less than or equal to 0 or
			is greater than {IOV_MAX}.

SEE ALSO
     fcntl(2), getsockopt(2), recv(2), select(2), socket(2), write(2)

HISTORY
     The send() function call appeared in 4.2BSD.

BSD					   May 9, 2008					      BSD


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