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.
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
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(0p) 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.
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.
The socket is already connected, and a specified option cannot
be set while the socket is connected.
The option is not supported by the protocol.
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
Insufficient resources are available in the system to complete
The following sections are informative.
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.
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
IEEE/The Open Group 2013 SETSOCKOPT(3P)