SEND(2)

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

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

int send(int s, const void *msg, int len, unsigned int flags);

int sendto(int s, const void *msg, int len, unsigned int flags, const struct sockaddr *to, int tolen);

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

DESCRIPTION
WARNING: This is a BSD man page. As of Linux 0.99.11, sendmsg was not implemented. 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, the error EMSGSIZE is returned, and the message is not transmitted. No indication of failure to deliver is implicit in a send. Locally detected errors are indicated by a return value of -1. If no messages 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. The select(2) call may be used to determine when it is possible to send more data. The flags parameter may include one or more of the following:
    #define	MSG_OOB        0x1  /* process out-of-band data */
    #define	MSG_DONTROUTE  0x4  /* bypass routing, use direct interface */
The flag MSG_OOB is used to send out-of-band data on sockets that support this notion (e.g. SOCK_STREAM); the underlying protocol must also support out-of-band data. MSG_DONTROUTE is usually used only by diagnostic or routing programs. See recv(2) for a description of the msghdr structure.

RETURN VALUES
The call returns the number of characters sent, or -1 if an error occurred.

ERRORS

EBADF
    An invalid descriptor was specified.

ENOTSOCK
    The argument s is not a socket.

EFAULT
    An invalid user space address was specified for a parameter.

EMSGSIZE
    The socket requires that message be sent atomically, and the size of the message to be sent made this impossible.

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

ENOBUFS
    The system was unable to allocate an internal buffer. The operation may succeed when buffers become available.

ENOBUFS
    The output queue for a network interface was full. This generally indicates that the interface has stopped sending, but may be caused by transient congestion.

CONFORMING TO
4.4BSD, SVr4 (these function calls appeared in 4.2BSD). The SVr4 versions docoment additional error conditions EINVAL, EINTR, EMSGSIZE, ENOSR, ENOMEM.

SEE ALSO
fcntl(2), recv(2), select(2), getsockopt(2), socket(2), write(2)