The send() function shall initiate transmission of a message from the
specified socket to its peer. The send() function shall send a message
only when the socket is connected (including when the peer of a connectionless
socket has been set via connect()).
The send() function takes the following arguments:
Specifies the socket file descriptor.
Points to the buffer containing the message to send.
Specifies the length of the message in bytes.
Specifies the type of message transmission. Values of this
argument are formed by logically OR'ing zero or more of the following
Terminates a record (if supported by the
Sends out-of-band data on sockets that support
out-of-band communications. The significance and semantics of out-of-band data
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() shall fail and no data shall be 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() 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, send() shall fail. The
select() and poll() 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.
The socket's file descriptor is marked O_NONBLOCK and the requested
operation would block.
The socket argument is not a valid file
A connection was forcibly closed by a peer.
The socket is not connection-mode and no peer address is set.
A signal interrupted send() before any data was
The message is too large to be sent all at once, as the
The socket is not connected or otherwise has not had the
The socket argument does not refer to a socket.
The socket argument is associated with a socket that
does not support one or more of the values set in flags.
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
The send() function may fail if:
The calling process does not have the appropriate
An I/O error occurred while reading from or writing to the
The local network interface used to reach the destination
No route to the network is present.
Insufficient resources were available in the system to
perform the operation.
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