sendto(2)                                                     sendto(2)

  send()

  NAME

    send(), sendto() - send a message from a socket

  SYNOPSIS

    #include 
    #include 

    ssize_t send (int s, const void *msg, size_t len, int flags)
    ssize_t sendto (int s, const void *msg, size_t len, int flags,
                    const struct sockaddr *to, int tolen)

  DESCRIPTION

    The send(2) and sendto(2) functions are used to transmit a message to
    another socket. The send(2) functionmay be used only when the socket is in
    a connected state, while sendto(2) 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(2). 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(2) 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:
    MSG_OOB           process out-of-band data

    MSG_DONTROUTE     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.

  RETURN VALUES

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

  ERRORS

    The send(2) and sendto(2) calls fail if:

    [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.

    [EAGAIN]
        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.

    [EISCONN]
        The AF_UNIX socket is already connected, and a destination address was
        specified.

  SEE ALSO

    fcntl(2)

    recv(2)

    select(2)

    getsockopt(2)

    socket(2)

    write(2)

  USAGE NOTES

    All of these functions are thread safe.

    All of these functions are async-signal safe.