PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SENDTO(3P)                POSIX Programmer's Manual               SENDTO(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       sendto — send a message on a socket

SYNOPSIS         top

       #include <sys/socket.h>

       ssize_t sendto(int socket, const void *message, size_t length,
           int flags, const struct sockaddr *dest_addr,
           socklen_t dest_len);

DESCRIPTION         top

       The sendto() function shall send a message through a connection-mode
       or connectionless-mode socket.

       If the socket is a connectionless-mode socket, the message shall be
       sent to the address specified by dest_addr if no pre-specified peer
       address has been set. If a peer address has been pre-specified,
       either the message shall be sent to the address specified by
       dest_addr (overriding the pre-specified peer address), or the
       function shall return −1 and set errno to [EISCONN].

       If the socket is connection-mode, dest_addr shall be ignored.

       The sendto() function takes the following arguments:

       socket      Specifies the socket file descriptor.

       message     Points to a buffer containing the message to be sent.

       length      Specifies the size 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 data. The significance
                                 and semantics of out-of-band data are
                                 protocol-specific.

                   MSG_NOSIGNAL  Requests not to send the SIGPIPE signal if
                                 an attempt to send is made on a stream-
                                 oriented socket that is no longer
                                 connected. The [EPIPE] error shall still be
                                 returned.

       dest_addr   Points to a sockaddr structure containing the destination
                   address. The length and format of the address depend on
                   the address family of the socket.

       dest_len    Specifies the length of the sockaddr structure pointed to
                   by the dest_addr argument.

       If the socket protocol supports broadcast and the specified address
       is a broadcast address for the socket protocol, sendto() shall fail
       if the SO_BROADCAST option is not set for the socket.

       The dest_addr argument specifies the address of the target.

       The length argument specifies the length of the message.

       Successful completion of a call to sendto() 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, sendto() shall block 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, sendto() shall fail.

       The socket in use may require the process to have appropriate
       privileges to use the sendto() function.

RETURN VALUE         top

       Upon successful completion, sendto() shall return the number of bytes
       sent. Otherwise, −1 shall be returned and errno set to indicate the
       error.

ERRORS         top

       The sendto() function shall fail if:

       EAFNOSUPPORT
              Addresses in the specified address family cannot be used with
              this socket.

       EAGAIN or EWOULDBLOCK
              The socket's file descriptor is marked O_NONBLOCK and the
              requested operation would block.

       EBADF  The socket argument is not a valid file descriptor.

       ECONNRESET
              A connection was forcibly closed by a peer.

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

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

       ENOTCONN
              The socket is connection-mode but is not connected.

       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 is no longer connected. In the latter
              case, and if the socket is of type SOCK_STREAM or
              SOCK_SEQPACKET and the MSG_NOSIGNAL flag is not set, the
              SIGPIPE signal is generated to the calling thread.

       If the address family of the socket is AF_UNIX, then sendto() shall
       fail if:

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

       ELOOP  A loop exists in symbolic links encountered during resolution
              of the pathname in the socket address.

       ENAMETOOLONG
              The length of a component of a pathname is longer than
              {NAME_MAX}.

       ENOENT A component of the pathname does not name an existing file or
              the pathname is an empty string.

       ENOTDIR
              A component of the path prefix of the pathname in the socket
              address names an existing file that is neither a directory nor
              a symbolic link to a directory, or the pathname in the socket
              address contains at least one non-<slash> character and ends
              with one or more trailing <slash> characters and the last
              pathname component names an existing file that is neither a
              directory nor a symbolic link to a directory.

       The sendto() function may fail if:

       EACCES Search permission is denied for a component of the path
              prefix; or write access to the named socket is denied.

       EDESTADDRREQ
              The socket is not connection-mode and does not have its peer
              address set, and no destination address was specified.

       EHOSTUNREACH
              The destination host cannot be reached (probably because the
              host is down or a remote router cannot reach it).

       EINVAL The dest_len argument is not a valid length for the address
              family.

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

       EISCONN
              A destination address was specified and the socket is already
              connected.

       ENETDOWN
              The local network 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.

       ENOMEM Insufficient memory was available to fulfill the request.

       If the address family of the socket is AF_UNIX, then sendto() may
       fail if:

       ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during
              resolution of the pathname in the socket address.

       ENAMETOOLONG
              The length of a pathname exceeds {PATH_MAX}, or pathname
              resolution of a symbolic link produced an intermediate result
              with a length that exceeds {PATH_MAX}.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       The select() and poll() functions can be used to determine when it is
       possible to send more data.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       getsockopt(3p), poll(3p), pselect(3p), recv(3p), recvfrom(3p),
       recvmsg(3p), send(3p), sendmsg(3p), setsockopt(3p), shutdown(3p),
       socket(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_socket.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                          SENDTO(3P)

Pages that refer to this page: netinet_in.h(0p)sys_socket.h(0p)recv(3p)recvfrom(3p)recvmsg(3p)send(3p)sendmsg(3p)shutdown(3p)