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 argument.
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.
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 original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
