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SETSOCKOPT(3P)             POSIX Programmer's Manual            SETSOCKOPT(3P)
PROLOG
       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
       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_RCV-
       TIMEO  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 set-
       sockopt() 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.1-2008,  <netinet_in.h>,
       <sys_socket.h>
COPYRIGHT
       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 Electri-
       cal 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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                       SETSOCKOPT(3P)