send(2) System Calls Manual send(2)
NAME
send - Sends 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
compatibility (see standards(5)):
int send (
int socket, char *message, int length, int flags );
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
send(): 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 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 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 sys-
tem 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 appropriate privileges.
NOTES
[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).
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 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 destination network is
unreachable. Insufficient resources were available in the system to complete the call. The available STREAMS resources were insuf-
ficient 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.
RELATED INFORMATION
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) delim off
send(2)