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

NAME

send - send a message on a socket

SYNOPSIS

cc [ flag ... ] file ... -lxnet [ library ... ]
#include <sys/socket.h>

ssize_t send(int socket, const void *buffer, size_t length, int flags);

PARAMETERS

socket
Specifies the socket file descriptor.


buffer
Points to the buffer containing the message to send.


length
Specifies the length 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 communications. 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 send() function initiates transmission of a message from the
specified socket to its peer. The send() function sends a message
only when the socket is connected (including when the peer of a
connectionless socket has been set via connect(3XNET)).


The length of the message to be sent is specified by the length
argument. If the message is too long to pass through the underlying
protocol, send() fails and no data is transmitted.


Successful completion of a call to send() 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, send() 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,
send() will fail. The select(3C) and poll(2) functions can be used to
determine when it is possible to send more data.


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

USAGE

The send() function is identical to sendto(3XNET) with a null pointer
dest_len argument, and to write() if no flags are used.

RETURN VALUES

Upon successful completion, send() 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 send() function will fail if:

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
The socket argument refers to a connection oriented
socket and the connection was forcibly closed by the
peer and is no longer valid. I/O can no longer be
performed to filedes.


EDESTADDRREQ
The socket is not connection-mode and no peer address
is set.


EFAULT
The buffer parameter can not be accessed.


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


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


ENOTCONN
The socket is not connected or otherwise has not had
the peer prespecified.


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.


The send() function may fail if:

EACCES
The calling process does not have the appropriate
privileges.


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


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.


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

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), connect(3XNET), getsockopt(3XNET), recv(3XNET),
recvfrom(3XNET), recvmsg(3XNET), sendmsg(3XNET), sendto(3XNET),
setsockopt(3XNET), shutdown(3XNET), socket(3XNET), tcp(4P),
attributes(7), standards(7)

September 10, 2018 SEND(3XNET)