send - Send messages on a socket
const void *buffer,
int flags );
[Tru64 UNIX] The following definition of the send() function
does not conform to current standards and is supported
only for backward compatibility (see standards(5)):
int flags );
Interfaces documented on this reference page conform to
industry standards as follows:
send(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies the unique name for the socket. Points to the
buffer containing the message to send. Specifies the
length of the message in bytes. Allows the sender to control
the transmission of the message. The flags parameter
to send a call is formed by logically ORing the values
shown in the following list, defined in the sys/socket.h
header file: Sends out-of-band data on sockets that support
out-of-band communication. Sends without using routing
tables. (Not recommended, for debugging purposes
The send() function sends a message only when the socket
is connected (this includes when the peer of a connectionless
socket has been set with a connect() call). The
sendto() and sendmsg() functions can be used with unconnected
or connected sockets.
Specify the length of the message with the length parameter.
If the message is too long to pass through the underlying
protocol, the system returns an error and does not
transmit the message.
No indication of failure to deliver is implied in a send()
function. A return value of -1 indicates only locally
If no space for messages is available at the sending
socket to hold the message to be transmitted, the send()
function blocks unless the socket is in a nonblocking I/O
mode. Use the select() function to determine when it is
possible to send more data.
The socket in use may also require that the calling process
have appropriate privileges.
[Tru64 UNIX] The send() function is identical to the
sendto() function with a zero-valued dest_len parameter,
and to the write() function if no flags are used. For that
reason, the send() function is disabled when 4.4BSD behavior
is enabled (that is, when the _SOCKADDR_LEN compiletime
option is defined).
Upon successful completion, the send() function returns
the number of characters sent. Otherwise, a value of -1 is
returned and errno is set to indicate the error.
If the send() function fails, errno may be set to one of
the following values: The calling proces does not have the
appropriate privileges. The message cannot be delivered
because of information label float restrictions. The
socket parameter is not valid. A connection was forcibly
closed by a peer. The socket is not connection-oriented
and no peer address is set. The buffer parameter cannot
[Tru64 UNIX] The message parameter is not in a
readable or writable part of the user address
space. A signal interrupted send before any data
was transmitted. An I/O error occurred while reading
from or writing to the file system. The message
is too large to be sent all at once, as the
socket requires. The local network connection is
not operational. The destination network is
unreachable. Insufficient resources were available
in the system to complete the call. The available
STREAMS resources were insufficient for the operation
to complete. The socket is not connected or
otherwise has not had the peer prespecified. The
socket parameter refers to a file, not 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-oriented and the peer is
closed or shut down for reading. In the latter
case, and if the socket is of type SOCK_STREAM, the
SIGPIPE signal is generated to the calling process.
The socket is marked nonblocking, and no space is
available for the send() function.
Functions: connect(2), getsockopt(2), poll(2), recv(2),
recvfrom(2), recvmsg(2), select(2), sendmsg(2), sendto(2),
setsockopt(2), shutdown(2), socket(2),
Network Programmer's Guide
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