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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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SETSOCKOPT(3P) POSIX Programmer's Manual SETSOCKOPT(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.
setsockopt — set the socket options
#include <sys/socket.h>
int setsockopt(int socket, int level, int option_name,
const void *option_value, socklen_t option_len);
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(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.
Upon successful completion, setsockopt() shall return 0.
Otherwise, -1 shall be returned and errno set to indicate the
error.
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.
None.
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.
None.
None.
Section 2.10, Sockets, bind(3p), endprotoent(3p), getsockopt(3p),
socket(3p)
The Base Definitions volume of POSIX.1‐2017, netinet_in.h(0p),
sys_socket.h(0p)
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(3P)
Pages that refer to this page: netinet_in.h(0p), netinet_tcp.h(0p), sys_socket.h(0p), getsockopt(3p), if_freenameindex(3p), if_indextoname(3p), if_nameindex(3p), if_nametoindex(3p), send(3p), sendmsg(3p), sendto(3p), shutdown(3p), socket(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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