Tribblix: manual page: sendto.3xnet

SENDTO(3XNET) X/Open Networking Services Library Functions SENDTO(3XNET)

NAME

sendto - send a message on a socket

SYNOPSIS

cc [ flag... ] file... -lxnet [ library ... ]
#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 sends a message through a connection-mode or
connectionless-mode socket. If the socket is connectionless-mode,
the message will be sent to the address specified by dest_addr. If
the socket is connection-mode, dest_addr is ignored.

If the socket protocol supports broadcast and the specified address
is a broadcast address for the socket protocol, sendto() will 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() blocks 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() will fail.

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

PARAMETERS

The 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.

MSG_NOSIGNAL
Don't generate the SIGPIPE signal when a
stream-oriented socket is no longer
connected.

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.

USAGE

The select(3C) and poll(2) functions can be used to determine when it
is possible to send more data.

RETURN VALUES

Upon successful completion, sendto() returns the number of bytes
sent. Otherwise, -1 is returned and errno is set to indicate the
error.

ERRORS

In addition to the errors documented below, an asynchronous error
generated by the underlying socket protocol may be returned. For the
full list of errors, please see the corresponding socket protocol
manual page. For example, for a list of TCP errors, please see
tcp(4P).

The sendto() function will fail if:

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

EAGAIN
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.

EFAULT
The message or destaddr parameter cannot be
accessed.

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 unless the MSG_NOSIGNAL flag is set.

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

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.

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.

ENETDOWN
The local 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.

ENOSR
There were insufficient STREAMS resources available
for the operation to complete.

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

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

ATTRIBUTES