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sendto(2)
NAME
  sendto - Sends messages through 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,
	  size_t dest_len );

  [Digital]  The following definition of the sendto() function	does not
  conform to current standards and is supported only for backward
  compatibility (see standards(5)):

  #include <sys/socket.h>
  int sendto (
	  int socket,
	  char *message_addr,
	  int length,
	  int flags,
	  struct sockaddr *dest_addr,
	  int dest_len );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  sendto():  XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  socket    Specifies the unique name for the socket.

  message   Points to the address containing the message to be sent.

  length    Specifies the size of the message in bytes.

  flags	    Allows the sender to control the message transmission.  The flags
	    value to send a call is formed by logically ORing the following
	    values, defined in the sys/socket.h file:

	    MSG_OOB   Processes out-of-band data on sockets that support
		      out-of-band data.

	    MSG_DONTROUTE
		      Sends without using routing tables.  (Not recommended,
		      for debugging purposes only.)

  dest_addr Points to a sockaddr structure, the format of which is determined
	    by the domain and by the behavior requested for the socket.	 The
	    sockaddr structure is an overlay for a sockaddr_in or sockaddr_un
	    structure, depending on which of the supported address families
	    is active.

	    [Digital] If the compile-time option _SOCKADDR_LEN is defined
	    before the sys/socket.h header file is included, the sockaddr
	    structure takes 4.4BSD behavior, with a field for specifying the
	    length of the socket address.  Otherwise, the default 4.3BSD
	    sockaddr structure is used, with the length of the socket address
	    assumed to be 14 bytes or less.

	    If _SOCKADDR_LEN is defined, the 4.3BSD sockaddr structure is
	    defined with the name osockaddr.

  dest_len  Specifies the length of the sockaddr structure pointed to by the
	    dest_addr parameter.

DESCRIPTION
  The sendto() function allows an application program to send messages
  through an unconnected socket by specifying a destination address.

  To broadcast on a socket, issue a setsockopt() function using the
  SO_BROADCAST option to gain broadcast permissions.

  Use the dest_addr parameter to provide the address of the target.  Specify
  the length of the message with the length parameter.

  If the sending socket has no space to hold the message to be transmitted,
  the sendto() function blocks unless the socket is in a nonblocking I/O
  mode.

  Use the select() function to determine when it is possible to send more
  data.

RETURN VALUES
  Upon successful completion, the sendto() function returns the number of
  characters sent.  Otherwise, a value of -1 is returned, and errno is set to
  indicate the error.

ERRORS
  If the sendto() function fails, errno may be set to one of the following
  values:

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

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

  [EBADF]   The socket parameter is not valid.

  [ECONNRESET]
	    A connection was forcibly closed by a peer.

  [EFAULT]  The dest_addr parameter is not in a writable part of the user
	    address space.

  [EINTR]   A signal interrupted sendto before any data was transmitted.

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

  [ELOOP]   Too many symbolic links were encountered in translating the
	    pathname in the socket address.

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

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

  [ENOTCONN]
	    The socket is connection-oriented but is not connected.

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

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

  [ENOTSOCK]
	    The socket parameter refers to a file, not a socket.

  [EPIPE]   The socket is shut down for writing, or the socket is
	    connection-oriented and the peer is closed or shut down for
	    reading. In the latter case, and if the socket is of type
	    SOCK_STREAM, the SIGPIPE signal is generated to the calling
	    process.

  [EWOULDBLOCK]
	    The socket is marked nonblocking, and no space is available for
	    the sendto() function.

RELATED INFORMATION
  Functions: recv(2), recvfrom(2), recvmsg(2), send(2), sendmsg(2),
  shutdown(2), socket(2), select(2), getsockopt(2), setsockopt(2)

  Standards: standards(5)