SETSOCKOPT(3P) POSIX Programmer's Manual SETSOCKOPT(3P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing 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 argu-
ment, to the value pointed to by the option_value argument for the socket associated with the file descriptor specified by the socket argu-
ment.
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 exam-
ple, 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 set-
ting 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 set-
sockopt() 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.1-2008, <netinet_in.h>, <sys_socket.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
ogy -- 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 Stan-
dard 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 https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE
/The Open Group 2013 SETSOCKOPT(3P)