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_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(3POSIX)