Section: POSIX Programmer's Manual (3P)
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.
--- set the socket options
int setsockopt(int socket, int level, int option_name,
const void *option_value, socklen_t option_len);
function shall set the option specified by the
argument, at the protocol level specified by the
argument, to the value pointed to by the
argument for the socket associated with the file descriptor specified
argument specifies the protocol level at which the option resides. To
set options at the socket level, specify the
argument as SOL_SOCKET. To set options at other levels, supply the
identifier for the protocol controlling the option. For example, to
indicate that an option is interpreted by the TCP (Transport Control
to IPPROTO_TCP as defined in the
argument specifies a single option to set. It can be one of the
socket-level options defined in
and described in
Section 2.10.16, Use of Options.
is equal to SO_RCVTIMEO or SO_SNDTIMEO and the implementation supports
setting the option, it is unspecified whether the
pointed to by
is stored as provided by this function or is rounded up to align with
the resolution of the clock being used. If
is called with
equal to SO_ACCEPTCONN, SO_ERROR, or SO_TYPE, the behavior is unspecified.
Upon successful completion,
shall return 0. Otherwise, -1 shall be returned and
set to indicate the error.
function shall fail if:
argument is not a valid file descriptor.
The send and receive timeout values are too big to fit into the timeout
fields in the socket structure.
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.
argument does not refer to a socket.
function may fail if:
There was insufficient memory available for the operation to complete.
Insufficient resources are available in the system to complete the
The following sections are informative.
function provides an application program with the means to control
socket behavior. An application program can use
to allocate buffer space, control timeouts, or permit socket data
header defines the socket-level options available to
Options may exist at multiple protocol levels. The SO_ options are
always present at the uppermost socket level.
The Base Definitions volume of POSIX.1-2017,
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
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