SENDMSG(3XNET) X/Open Networking Services Library Functions SENDMSG(3XNET)
NAME
sendmsg - send a message on a socket using a message structure
SYNOPSIS
cc [
flag ... ]
file ...
-lxnet [
library ... ]
#include <sys/socket.h>
ssize_t sendmsg(
int socket,
const struct msghdr *message,
int flags);
PARAMETERS
The function takes the following arguments:
socket Specifies the socket file descriptor.
message Points to a
msghdr structure, containing both the destination
address and the buffers for the outgoing message. The length
and format of the address depend on the address family of the
socket. The
msg_flags member is ignored.
flags Specifies the type of message transmission. The application
may specify 0 or the following flag:
MSG_EOR Terminates a record (if supported by the protocol)
MSG_OOB Sends out-of-band data on sockets that support out-
of-bound 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.
DESCRIPTION
The
sendmsg() 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
msghdr. If the socket
is connection-mode, the destination address in
msghdr is ignored.
The
msg_iov and
msg_iovlen fields of message specify zero or more
buffers containing the data to be sent.
msg_iov points to an array of
iovec structures;
msg_iovlen must be set to the dimension of this array.
In each
iovec structure, the
iov_base field specifies a storage area
and the
iov_len field gives its size in bytes. Some of these sizes can
be zero. The data from each storage area indicated by
msg_iov is sent in
turn.
Successful completion of a call to
sendmsg() 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,
sendmsg() function 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,
sendmsg() function
will fail.
If the socket protocol supports broadcast and the specified address is a
broadcast address for the socket protocol,
sendmsg() will fail if the
SO_BROADCAST option is not set for the socket.
The socket in use may require the process to have appropriate privileges
to use the
sendmsg() function.
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,
sendmsg() function 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
sendmsg() function will fail if:
EAGAIN EWOULDBLOCK The socket's file descriptor is marked O_NONBLOCK and the
requested operation would block.
EAFNOSUPPORT Addresses in the specified address family cannot be used
with this socket.
EBADF The
socket argument is not a valid file descriptor.
ECONNRESET A connection was forcibly closed by a peer.
EFAULT The
message parameter, or storage pointed to by the
msg_name,
msg_control or
msg_iov fields of the
message parameter, or storage pointed to by the
iovec structures
pointed to by the
msg_iov field can not be accessed.
EINTR A signal interrupted
sendmsg() before any data was
transmitted.
EINVAL The sum of the
iov_len values overflows an
ssize_t.
EMSGSIZE The message is to large to be sent all at once (as the
socket requires), or the
msg_iovlen member of the
msghdr structure pointed to by
message is less than or equal to
0 or is greater than
IOV_MAX.
ENOTCONN The socket is connection-mode but is not connected.
ENOTSOCK The
socket argument does not refer 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
sendmsg() 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
sendmsg() 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).
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
sendmsg() may fail
if:
ENAMETOOLONG Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds
PATH_MAX.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
SEE ALSO
poll(2) select(3C),
getsockopt(3XNET),
recv(3XNET),
recvfrom(3XNET),
recvmsg(3XNET),
send(3XNET),
sendto(3XNET),
setsockopt(3XNET),
shutdown(3XNET),
socket(3XNET),
tcp(4P),
attributes(7),
standards(7) September 10, 2018
SENDMSG(3XNET)