NAME

send − send a message on a socket

SYNOPSIS

cc [ flag ... ] file ... −lxnet [ library ... ]

#include <sys/socket.h>

ssize_t send(int socket, const void ∗buffer, size_t length, int flags);

DESCRIPTION

The send() function initiates transmission of a message from the specified socket to its peer.  The send() function sends a message only when the socket is connected.  This function takes the following arguments:

socket Specifies the socket file descriptor. 

buffer Points to the buffer containing the message to send. 

length Specifies the length of the message in bytes. 

flags Specifies the type of message transmission.  Values of this argument are formed by logically OR ’ing zero or more of the following flags:

MSG_EOR Terminates a record (if supported by the protocol)

MSG_OOB Sends out-of-band data on sockets that support out-of-band communications.  The significance and semantics of out-of-band data are protocol-specific. 

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() fails and no data is 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() blocks 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() will fail.  The select(3C) and poll(2) functions can be used to determine when it is possible to send more data. 

RETURN VALUES

Upon successful completion, send() returns the number of bytes sent.  Otherwise, −1 is returned and errno is set to indicate the error. 

ERRORS

The send() function will fail if:

EBADF The socket argument is not a valid file descriptor. 

ECONNRESET
A connection was forcibly closed by a peer.

EDESTADDRREQ
The socket is not connection-mode and no peer address is set.

EINTR A signal interrupted send() before any data was transmitted. 

EMSGSIZE The message is too large be sent all at once, as the socket requires. 

ENOTCONN The socket is not connected or otherwise has not had the peer prespecified. 

ENOTSOCK The socket argument does not refer to a socket. 

EOPNOTSUPP
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-mode 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. 

EAGAIN The socket’s file descriptor is marked O_NONBLOCK and the requested operation would block.  The send() function may fail if:

ENETDOWN The local interface used to reach the destination is down. 

ENETUNREACH
No route to the network is present.

ENOBUFS Insufficient resources were available in the system to perform the operation. 

ENOSR There were insufficient STREAMS resources available for the operation to complete. 

EIO An I/O error occurred while reading from or writing to the file system. 

USAGE

The send() function is identical to sendto(3XN) with a null pointer dest_len argument, and to write(2) if no flags are used. 

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

SEE ALSO

poll(2), connect(3XN), getsockopt(3XN), recv(3XN), recvfrom(3XN), recvmsg(3XN), select(3C), sendmsg(3XN), sendto(3XN), setsockopt(3XN), shutdown(3XN), socket(3XN), attributes(5), socket(5)

SunOS 5.6  —  Last change: 16 May 1997