send(3N)

send a message from a socket

From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.

Also by this name: send(1L), Extra programs: news, mail, languages, tools

NAME

send, sendto, sendmsg - send a message from a socket

SYNOPSIS

#include <sys/types.h>
#include <sys/socket.h>

int send(s, msg, len, flags)
int s;
char *msg;
int len, flags;

int sendto(s, msg, len, flags, to, tolen)
int s;
char *msg;
int len, flags;
struct sockaddr *to;
int tolen;

int sendmsg(s, msg, flags)
int s;
struct msghdr *msg;
int flags;

DESCRIPTION

s is a socket created with socket(3N). send(), sendto(), and sendmsg() are used to transmit a message to another socket. send() may be used only when the socket is in a connected state, while sendto() and sendmsg() may be used at any time.

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.

No indication of failure to deliver is implicit in a send(). Return values of -1 indicate some locally detected errors.

If no buffer space is available at the socket to hold the message to be transmitted, then send() normally blocks, unless the socket has been placed in non-blocking I/O mode (see fcntl(2)). The select() call may be used to determine when it is possible to send more data.

The flags parameter is formed by ORing one 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. Currently, only SOCK_STREAM sockets created in the AF_INET address family 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.

See recv(3N) for a description of the msghdr structure.

RETURN VALUE

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

ERRORS

The calls fail if:

EBADF s is an invalid descriptor.

ENOTSOCK s is a descriptor for a file, not a socket.

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

EINTR               The   operation   was   interrupted   by
                    delivery  of  a  signal  before any data
                    could be buffered to be sent.

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

EWOULDBLOCK The socket is marked non-blocking and the requested operation would block.

ENOMEM There was insufficient user memory available for the operation to complete.