NAME

setsockopt − set the socket options

SYNOPSIS

cc [ flag ... ] file ... −lxnet [ library ... ]

#include <sys/socket.h>

int setsockopt(int socket, int level, int option_name, const void ∗option_value,

size_t option_len);

DESCRIPTION

The setsockopt() function sets 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 protocol number for the protocol controlling the option.  For example, to indicate that an option will be interpreted by the TCP (Transport Control Protocol), set level to the protocol number of TCP , as defined in the <netinet/in.h> header, or as determined by using getprotobyname(3XN). 

The option_name argument specifies a single option to set.  The option_name argument and any specified options are passed uninterpreted to the appropriate protocol module for interpretations.  The <sys/socket.h> header defines the socket level options.  The socket level options can be enabled or disabled.  The options are as follows:

SO_DEBUG Turns on recording of debugging information.  This option enables or disables debugging in the underlying protocol modules.  This option takes an int value. 

SO_BROADCAST
Permits sending of broadcast messages, if this is supported by the protocol. This option takes an int value. 

SO_REUSEADDR
Specifies that the rules used in validating addresses supplied to bind(3XN) should allow reuse of local addresses, if this is supported by the protocol.  This option takes an int value. 

SO_KEEPALIVE
Keeps connections active by enabling the periodic transmission of messages, if this is supported by the protocol.  This option takes an int value. 

If the connected socket fails to respond to these messages, the connection is broken and processes writing to that socket are notified with a SIGPIPE signal. 

SO_LINGER Lingers on a close(2) if data is present.  This option controls the action taken when unsent messages queue on a socket and close(2) is performed.  If SO_LINGER is set, the system blocks the process during close(2) until it can transmit the data or until the time expires.  If SO_LINGER is not specified, and close(2) is issued, the system handles the call in a way that allows the process to continue as quickly as possible.  This option takes a linger structure, as defined in the <sys/socket.h> header, to specify the state of the option and linger interval. 

SO_OOBINLINE
Leaves received out-of-band data (data marked urgent) in line. This option takes an int value. 

SO_SNDBUF Sets send buffer size.  This option takes an int value. 

SO_RCVBUF Sets receive buffer size.  This option takes an int value. 

For boolean options, 0 indicates that the option is disabled and 1 indicates that the option is enabled. 

Options at other protocol levels vary in format and name. 

RETURN VALUES

Upon successful completion, setsockopt() returns 0.  Otherwise, −1 is returned and errno is set to indicate the error. 

ERRORS

The setsockopt() function will fail if:

EBADF The socket argument is not a valid file descriptor. 

EINVAL The specified option is invalid at the specified socket level or the socket has been shut down. 

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. 

ENOSR There were insufficient STREAMS resources available for the operation to complete. 

USAGE

The setsockopt() function provides an application program with the means to control socket behaviour.  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. 

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

SEE ALSO

bind(3XN), endprotoent(3XN), getsockopt(3XN), socket(3XN), attributes(5), socket(5)

SunOS 5.6  —  Last change: 16 May 1997