2.4 Socket Options

The socket options supported by Windows Sockets are listed in the pages describing setsockopt() and getsockopt(). A Windows Sockets implementation must recognize all of these options, and (for getsockopt()) return plausible values for each. The default value for each option is shown in the following table.

Value	Type	Meaning	Default	Note
SO_ACCEPTCONN	BOOL	Socket is listen()ing.	FALSE unless a listen() has been performed
SO_BROADCAST	BOOL	Socket is configured for the transmission of broadcast messages.	FALSE
SO_DEBUG	BOOL	Debugging is enabled.	FALSE	(i)
SO_DONTLINGER	BOOL	If true, the SO_LINGER option is disabled.	TRUE
SO_DONTROUTE	BOOL	Routing is disabled.	FALSE	(i)
SO_ERROR	int	Retrieve error status and clear.	0
SO_KEEPALIVE	BOOL	Keepalives are being sent.	FALSE
SO_LINGER	struct linger FAR *	Returns the current linger options.	l_onoff is 0
SO_OOBINLINE	BOOL	Out-of-band data is being received in the normal data stream.	FALSE
SO_RCVBUF	int	Buffer size for receives	Implementation dependent	(i)
SO_REUSEADDR	BOOL	The address to which this socket is bound can be used by others.	FALSE
SO_SNDBUF	int	Buffer size for sends	Implementation dependent	(i)
SO_TYPE	int	The type of the socket (e.g. SOCK_STREAM).	As created via socket()
TCP_NODELAY	BOOL	Disables the Nagle algorithm for send coalescing.	Implementation dependent

Notes:

(i) An implementation may silently ignore this option on setsockopt() and return a constant value for getsockopt(), or it may accept a value for setsockopt() and return the corresponding value in getsockopt() without using the value in any way.