send - Sends messages on a socket
ssize_t send (
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 compatibil-
ity (see standards(5)):
int send (
int flags );
Interfaces documented on this reference page conform to industry standards
Refer to the standards(5) reference page for more information about indus-
try standards and associated tags.
socket Specifies the unique name for the socket.
buffer Points to the buffer containing the message to send.
length Specifies the length of the message in bytes.
flags 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:
MSG_OOB Sends out-of-band data on sockets that support out-of-
Sends without using routing tables. (Not recommended,
for debugging purposes only.)
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 con-
nect() call). The sendto() and sendmsg() functions can be used with uncon-
nected or connected sockets.
Specify the length of the message with the length parameter. If the mes-
sage 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 detected errors.
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 appropri-
[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 compile-time
option is defined).
Upon successful completion, the send() function returns the number of char-
acters 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
[EACCES] The calling proces does not have the appropriate privileges.
[EBADF] 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.
[EFAULT] The buffer parameter cannot be accessed.
[Tru64 UNIX] The message parameter is not in a readable or writ-
able part of the user address space.
[EINTR] A signal interrupted send before any data was transmitted.
[EIO] An I/O error occurred while reading from or writing to the file
The message is too large to be sent all at once, as the socket
The local network connection is not operational.
The destination network is unreachable.
[ENOBUFS] Insufficient resources were available in the system to complete
[ENOSR] The available STREAMS resources were insufficient for the opera-
tion to complete.
The socket is not connected or otherwise has not had the peer
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.
[EPIPE] The socket is shut down for writing, or the socket is
connection-oriented and the peer is closed or shut down for read-
ing. In the latter case, and if the socket is of type
SOCK_STREAM, the SIGPIPE signal is generated to the calling pro-
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),