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SENDTO(P)			    POSIX Programmer's Manual				SENDTO(P)

NAME
       sendto - send a message on a socket

SYNOPSIS
       #include <sys/socket.h>

       ssize_t sendto(int socket, const void *message, size_t length,
	      int flags, const struct sockaddr *dest_addr,
	      socklen_t dest_len);

DESCRIPTION
       The  sendto()  function	shall send a message through a connection-mode or connectionless-
       mode socket. If the socket is connectionless-mode,  the	message  shall	be  sent  to  the
       address	specified  by  dest_addr.  If  the  socket is connection-mode, dest_addr shall be
       ignored.

       The sendto() function takes the following arguments:

       socket Specifies the socket file descriptor.

       message
	      Points to a buffer containing the message to be sent.

       length Specifies the size of the message in bytes.

       flags  Specifies the type of message transmission. Values of this argument are  formed  by
	      logically OR'ing zero or more of the following flags:

       MSG_EOR
	      Terminates a record (if supported by the protocol).

       MSG_OOB
	      Sends  out-of-band  data on sockets that support out-of-band data. The significance
	      and semantics of out-of-band data are protocol-specific.

       dest_addr
	      Points to a sockaddr structure containing the destination address.  The length  and
	      format of the address depend on the address family of the socket.

       dest_len
	      Specifies  the  length  of the sockaddr structure pointed to by the dest_addr argu-
	      ment.

       If the socket protocol supports broadcast and the specified address is a broadcast address
       for the socket protocol, sendto() shall fail if the SO_BROADCAST option is not set for the
       socket.

       The dest_addr argument specifies the address of the target.  The length argument specifies
       the length of the message.

       Successful  completion of a call to sendto() does not guarantee delivery of the message. A
       return value of -1 indicates only locally-detected errors.

       If space is not available at the sending socket to hold the message to be transmitted  and
       the  socket file descriptor does not have O_NONBLOCK set, sendto() shall block until space
       is available.  If space is not available at the sending socket to hold the message  to  be
       transmitted and the socket file descriptor does have O_NONBLOCK set, sendto() shall fail.

       The  socket  in	use  may  require  the	process to have appropriate privileges to use the
       sendto() function.

RETURN VALUE
       Upon successful completion, sendto() shall return the number of bytes sent. Otherwise,  -1
       shall be returned and errno set to indicate the error.

ERRORS
       The sendto() function shall fail if:

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

       EAGAIN or EWOULDBLOCK
	      The socket's file descriptor is marked O_NONBLOCK and the requested operation would
	      block.

       EBADF  The socket argument is not a valid file descriptor.

       ECONNRESET
	      A connection was forcibly closed by a peer.

       EINTR  A signal interrupted sendto() before any data was transmitted.

       EMSGSIZE
	      The message is too large to be sent all at once, as the socket requires.

       ENOTCONN
	      The socket is connection-mode but is not connected.

       ENOTSOCK
	      The socket argument does not refer to a socket.

       EOPNOTSUPP
	      The socket argument is associated with a socket that does not support one  or  more
	      of the values set in flags.

       EPIPE  The  socket  is  shut  down for writing, or the socket is connection-mode and is no
	      longer connected. In the latter case, and if the socket is of type SOCK_STREAM, the
	      SIGPIPE signal is generated to the calling thread.

       If the address family of the socket is AF_UNIX, then sendto() shall fail if:

       EIO    An I/O error occurred while reading from or writing to the file system.

       ELOOP  A  loop  exists  in symbolic links encountered during resolution of the pathname in
	      the socket address.

       ENAMETOOLONG
	      A component of a pathname exceeded {NAME_MAX} characters,  or  an  entire  pathname
	      exceeded {PATH_MAX} characters.

       ENOENT A  component  of	the pathname does not name an existing file or the pathname is an
	      empty string.

       ENOTDIR
	      A component of the path prefix of the pathname in  the  socket  address  is  not	a
	      directory.

       The sendto() function may fail if:

       EACCES Search  permission is denied for a component of the path prefix; or write access to
	      the named socket is denied.

       EDESTADDRREQ
	      The socket is not connection-mode and does not have its peer address  set,  and  no
	      destination address was specified.

       EHOSTUNREACH
	      The  destination	host  cannot  be  reached (probably because the host is down or a
	      remote router cannot reach it).

       EINVAL The dest_len argument is not a valid length for the address family.

       EIO    An I/O error occurred while reading from or writing to the file system.

       EISCONN
	      A destination address was specified and the  socket  is  already	connected.   This
	      error may or may not be returned for connection mode sockets.

       ENETDOWN
	      The local network interface used to reach the destination is down.

       ENETUNREACH
	      No route to the network is present.

       ENOBUFS
	      Insufficient resources were available in the system to perform the operation.

       ENOMEM Insufficient memory was available to fulfill the request.

       If the address family of the socket is AF_UNIX, then sendto() may fail if:

       ELOOP  More  than  {SYMLOOP_MAX}  symbolic links were encountered during resolution of the
	      pathname in the socket address.

       ENAMETOOLONG
	      Pathname resolution of a symbolic link produced an intermediate result whose length
	      exceeds {PATH_MAX}.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The  select()  and  poll()  functions can be used to determine when it is possible to send
       more data.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       getsockopt() , poll() , recv() , recvfrom() , recvmsg() , select() , send() , sendmsg()	,
       setsockopt()    ,   shutdown()	,   socket()   ,   the	 Base	Definitions   volume   of
       IEEE Std 1003.1-2001, <sys/socket.h>

COPYRIGHT
       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					SENDTO(P)
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