NAME

send, sendto – send a message from a socket

SYNOPSIS

#include <sys/socket.h>

size_t send(int s ,

const void *msg ,

size_t len ,

int flags );

size_t sendto(int s ,

const void *msg ,

size_t len ,

int flags ,

const struct sockaddr *to,

socklen_t tolen );

DESCRIPTION

send() and sendto() are used to transmit a message to another transport end-point. send() may be used only when the socket is in a connected state, while sendto() may be used at any time. s is a socket created with socket().

The address of the target is given by to with tolen specifying its size. The length of the message is given by len . If the message is too long to pass atomically through the underlying protocol, then the error EMSGSIZE is returned, and the message is not transmitted.

A return value of -1 indicates locally detected errors only. It does not implicitly mean the message was not delivered.

If the socket does not have enough buffer space available to hold the message being sent, send() blocks. Non-blocking I/O mode is not supported in this case.

The flags parameter is formed from the bitwise OR of zero or more of the following:

MSG_OOB

Send out-of-band data on sockets that support this notion. The underlying protocol must also support out-of-band data. Only SOCK_STREAM sockets support out-of-band data.

MSG_DONTROUTE

The SO_DONTROUTE option is turned on for the duration of the operation. It is used only by diagnostic or routing programs.

MSG_DONTWAIT

Tells the appropriate socket operation to work in a non-blocking way.

RETURN VALUES

These calls return the number of bytes sent, or -1 if an error occurred.

ERRORS

This function is a member of Unison’s IOLIB family of functions. IOLIB is implemented as a message passing and generalized interface layer. Each Unison I/O server is responsible for its own error reporting.

For an exact list of error codes returned by a particular server, refer to that server’s documentation in the Unison Programmer’s Guide for each specific platform.

Servers may implement these errors codes in response to this function.

The calls fail if:

EBADF

s is an invalid file descriptor.

EINVAL

tolen is not the size of a valid address for the specified address family.

EMSGSIZE

The socket requires that message be sent atomically, and the message was too long.

ENOMEM

There was insufficient memory available to complete the operation.

ENOTSOCK

s is not a socket.

EAGAIN or EWOULDBLOCK

The socket’s file descriptor is marked O_NONBLOCK and the requested operation would block.

SEE ALSO

write(), connect(), getsockopt(), recv(), socket(), connect()