SETSOCKOPT(3)              POSIX Programmer's Manual             SETSOCKOPT(3)



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

NAME
       setsockopt -- set the socket options

SYNOPSIS
       #include <sys/socket.h>

       int setsockopt(int socket, int level, int option__name,
           const void *option__value, socklen_t option__len);

DESCRIPTION
       The setsockopt() function shall set the option specified by the
       option__name argument, at the protocol level specified by the level
       argument, to the value pointed to by the option__value argument for the
       socket associated with the file descriptor specified by the socket
       argument.

       The level argument specifies the protocol level at which the option
       resides. To set options at the socket level, specify the level argument
       as SOL_SOCKET. To set options at other levels, supply the appropriate
       level identifier for the protocol controlling the option. For example,
       to indicate that an option is interpreted by the TCP (Transport Control
       Protocol), set level to IPPROTO_TCP as defined in the <netinet/in.h>
       header.

       The option__name argument specifies a single option to set. It can be
       one of the socket-level options defined in <sys_socket.h> and described
       in Section 2.10.16, Use of Options.  If option__name is equal to
       SO_RCVTIMEO or SO_SNDTIMEO and the implementation supports setting the
       option, it is unspecified whether the struct timeval pointed to by
       option__value is stored as provided by this function or is rounded up to
       align with the resolution of the clock being used. If setsockopt() is
       called with option__name equal to SO_ACCEPTCONN, SO_ERROR, or SO_TYPE,
       the behavior is unspecified.

RETURN VALUE
       Upon successful completion, setsockopt() shall return 0. Otherwise, -1
       shall be returned and errno set to indicate the error.

ERRORS
       The setsockopt() function shall fail if:

       EBADF  The socket argument is not a valid file descriptor.

       EDOM   The send and receive timeout values are too big to fit into the
              timeout fields in the socket structure.

       EINVAL The specified option is invalid at the specified socket level or
              the socket has been shut down.

       EISCONN
              The socket is already connected, and a specified option cannot
              be set while the socket is connected.

       ENOPROTOOPT
              The option is not supported by the protocol.

       ENOTSOCK
              The socket argument does not refer to a socket.

       The setsockopt() function may fail if:

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

       ENOBUFS
              Insufficient resources are available in the system to complete
              the call.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The setsockopt() function provides an application program with the
       means to control socket behavior. An application program can use
       setsockopt() to allocate buffer space, control timeouts, or permit
       socket data broadcasts. The <sys/socket.h> header defines the socket-
       level options available to setsockopt().

       Options may exist at multiple protocol levels. The SO_ options are
       always present at the uppermost socket level.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.10, Sockets, bind(), endprotoent(), getsockopt(), socket()

       The Base Definitions volume of POSIX.1-2017, <netinet_in.h>,
       <sys_socket.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/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                  2017                        SETSOCKOPT(3)
