SETSOCKOPT
Section: POSIX Programmer's Manual (3P)
Updated: 2017
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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 .