send(2)send(2)NAMEsend - Send messages on a socket
SYNOPSIS
#include <sys/socket.h>
ssize_t send(
int socket,
const void *buffer,
size_t length,
int flags );
[Tru64 UNIX] The following definition of the send() function does not
conform to current standards and is supported only for backward compat‐
ibility (see standards(5)): int send(
int socket,
char *message,
int length,
int flags );
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
send(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Specifies the unique name for the socket. Points to the buffer con‐
taining 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 commu‐
nication. Sends without using routing tables. (Not recommended, for
debugging purposes only.)
DESCRIPTION
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 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 appro‐
priate privileges.
NOTES
[Tru64 UNIX] The send() function is identical to the sendto() func‐
tion 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 com‐
pile-time option is defined).
RETURN VALUES
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.
ERRORS
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 be accessed.
[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 destina‐
tion network is unreachable. Insufficient resources were avail‐
able 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 pre‐
specified. 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 non‐
blocking, and no space is available for the send() function.
SEE ALSO
Functions: connect(2), getsockopt(2), poll(2), recv(2), recvfrom(2),
recvmsg(2), select(2), sendmsg(2), sendto(2), setsockopt(2), shut‐
down(2), socket(2),
Standards: standards(5)
Network Programmer's Guide
send(2)
