setsockopt()

set options associated with a socket

Synopsis:

#include <sys/types.h>
#include <sys/socket.h>

int setsockopt( int s, 
                int level, 
                int optname, 
                const void *optval, 
                int optlen );

Description:

The setsockopt() function sets options associated with a socket. Options may exist at multiple protocol levels; they're always present at the uppermost ``socket'' level.

When manipulating a socket option, you must specify the option's name and the level at which the option resides:

• To manipulate options at the socket level, specify level as SOL_SOCKET.
• To manipulate options at any other level, supply the protocol number of the appropriate protocol controlling the option. For example, to indicate that an option is to be interpreted by the TCP protocol, you should set level to the protocol number of TCP; see getprotobyname().

The optval and optlen arguments specify the option's value and the value's length. If no option value is to be supplied, optval may be NULL. To enable a boolean option, specify a nonzero value for optval; to disable the option specify a value of 0.

The parameter optname and any specified options are passed uninterpreted to the appropriate protocol module for interpretation. The include file <sys/socket.h> contains definitions for socket-level options; for information about these options, see getsockopt(). Options at other protocol levels vary in format and name.

Returns:

0

Success.

-1

An error occurred; errno is set.

Errors:

If an error occurred, errno could contain one of the following:

EBADF

The argument s isn't a valid descriptor.

EDOM

Value was set out of range.

EFAULT

The address pointed to by optval isn't in a valid part of the process address space.

ENOPROTOOPT

The option is unknown at the level indicated.

Classification:

POSIX 1003.1g (draft)

See also:

ICMP, IP, TCP, and UDP protocols, getsockopt()