LPWSPSETSOCKOPT callback function (ws2spi.h)

Article
10/13/2021

The LPWSPSetSockOpt function sets a socket option.

Syntax

LPWSPSETSOCKOPT Lpwspsetsockopt;

int Lpwspsetsockopt(
  [in]  SOCKET s,
  [in]  int level,
  [in]  int optname,
  [in]  const char *optval,
  [in]  int optlen,
  [out] LPINT lpErrno
)
{...}

Parameters

[in] s

The descriptor that identifies a socket.

[in] level

The level at which the option is defined; the supported levels include SOL_SOCKET. For more information, see Winsock Annexes.

[in] optname

The socket option for which the value is to be set.

[in] optval

A pointer to the buffer in which the value for the requested option is supplied.

[in] optlen

The size, in bytes, of the optval buffer.

[out] lpErrno

A pointer to the error code.

Return value

If no error occurs, LPWSPSetSockOpt returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code is available in lpErrno.

Error Code	Meaning
WSAENETDOWN	The network subsystem has failed.
WSAEFAULT	The optval is not in a valid part of the process address space or optlen parameter is too small.
WSAEINPROGRESS	Function is invoked when a callback is in progress.
WSAEINPROGRESS	Blocking Windows Sockets call is in progress, or the service provider is still processing a callback function.
WSAEINVAL	The level is not valid, or the information in optval is not valid.
WSAENETRESET	The connection has been broken due to keep-alive activity detecting a failure while the operation was in progress.
WSAENOPROTOOPT	Option is unknown or unsupported for the specified provider.
WSAENOTCONN	The connection has been reset when SO_KEEPALIVE is set.
WSAENOTSOCK	The descriptor is not a socket.

Remarks

The LPWSPSetSockOpt function sets the current value for a socket option associated with a socket of any type, in any state. Although options can exist at multiple protocol levels, they are always present at the uppermost socket level. Options affect socket operations, such as whether broadcast messages can be sent on the socket.

There are two types of socket options: Boolean options that enable or disable a feature or behavior, and options that require an integer value or structure. To enable a Boolean option, optval points to a nonzero integer. To disable the option, optval points to an integer equal to zero. The optlen parameter should be equal to sizeof (int) for Boolean options. For other options, optval points to an integer or structure that contains the desired value for the option, and optlen is the length of the integer or structure.

For more information about socket options, see Socket Options.

level = SOL_SOCKET

Value	Type	Meaning
SO_BROADCAST	BOOL	Enables transmission and receipt of broadcast messages on the socket.
SO_DEBUG	BOOL	Records debugging information.
SO_DONTLINGER	BOOL	Reserved.
SO_DONTROUTE	BOOL	Disabled routing: send directly to an interface. Setting this socket option succeeds but is ignored on AF_INET sockets; fails on AF_INET6 sockets with WSAENOPROTOOPT . This option is not supported on ATM sockets (results in an error).
SO_GROUP_PRIORITY	int	Reserved.
SO_KEEPALIVE	BOOL	Sends keep-alives. Not supported on ATM sockets (results in an error).
SO_LINGER	struct linger	Lingers on close if unsent data is present.
SO_OOBINLINE	BOOL	Receives OOB data in the normal data stream.
SO_RCVBUF	int	Specifies the total per-socket buffer space reserved for receives. This is unrelated to SO_MAX_MSG_SIZE and does not necessarily correspond to the size of the TCP receive window.
SO_REUSEADDR	BOOL	Allows the socket to be bound to an address that is already in use. (See Bind.) Not applicable on ATM sockets.
SO_SNDBUF	int	Specifies the total per-socket buffer space reserved for sends. This is unrelated to SO_MAX_MSG_SIZE and does not necessarily correspond to the size of a TCP send window.
PVD_CONFIG	Service Provider Dependent	This object stores the configuration information for the service provider associated with socket s. The exact format of this data structure is service provider specific.

Calling LPWSPGetSockopt with an unsupported option will result in an error code of WSAENOPROTOOPT returned in lpErrno.

SO_DEBUG

Windows Sockets service providers are encouraged, but not required, to supply output debug information if the SO_DEBUG option is set by a Windows Sockets SPI client. The mechanism for generating the debug information and the format are beyond the scope of this specification.

SO_GROUP_PRIORITY

Reserved.

SO_KEEPALIVE

A Windows Sockets SPI client can request that a TCP/IP provider enable the use of keep-alive packets on TCP connections by turning on the SO_KEEPALIVE socket option. A Windows Sockets provider need not support the use of keep-alives: if it does, the precise semantics are implementation specific, but should conform to section 4.2.3.6 of RFC 1122: Requirements for Internet Hosts—Communication Layers. (This resource may only be available in English.) If a connection is dropped as the result of keep-alive the error code WSAENETRESET is returned to any calls in progress on the socket, and any subsequent calls will fail with WSAENOTCONN .

SO_LINGER

SO_LINGER controls the action taken when unsent data is queued on a socket and a LPWSPCloseSocket is performed. See LPWSPCloseSocket for a description of the way in which the SO_LINGER settings affect the semantics of LPWSPCloseSocket. The Windows Sockets SPI client sets the desired behavior by creating a LINGER structure, pointed to by the optval parameter, with the following elements.

struct linger {
  u_short l_onoff;
  u_short l_linger;
}

To enable SO_LINGER, a Windows Sockets SPI client should set l_onoff to a nonzero value, set l_linger to zero or the desired time-out, in seconds, and call LPWSPSetSockOpt. To enable SO_DONTLINGER, that is, disable SO_LINGER, l_onoff should be set to zero and LPWSPSetSockOpt should be called. Be aware that enabling SO_LINGER with a nonzero time-out on a nonblocking socket is not recommended. For more information, see LPWSPCloseSocket.

Enabling SO_LINGER also disables SO_DONTLINGER, and vice versa. Be aware that if SO_DONTLINGER is disabled (that is, SO_LINGER is enabled) then no time-out value is specified. In this case, the time-out used is implementation dependent. If a previous time-out has been established for a socket (by enabling SO_LINGER), then this time-out value should be reinstated by the service provider.

SO_REUSEADDR

By default, a socket cannot be bound (for more information, see LPWSPBind) to a local address that is already in use. On occasion, however, it may be desirable to reuse an address in this way. Because every connection is uniquely identified by the combination of local and remote addresses, there is no problem with having two sockets bound to the same local address as long as the remote addresses are different. To inform the Windows Sockets provider that a LPWSPBind on a socket should be allowed to bind to a local address that is already in use by another socket, the Windows Sockets SPI client should set the SO_REUSEADDR socket option for the socket before issuing the LPWSPBind. Be aware that the option is interpreted only at the time of the LPWSPBind: it is therefore unnecessary, but harmless, to set the option on a socket that is not to be bound to an existing address, and setting or resetting the option after the LPWSPBind has no effect on this or any other socket.

SO_SNDBUF

When a Windows Sockets implementation supports the SO_RCVBUF and SO_SNDBUF options, a Windows Sockets SPI client can request different buffer sizes (larger or smaller). The call can succeed even though the service provider did not make available the entire amount requested. A Windows Sockets SPI client must call LPWSPGetSockopt with the same option to verify the buffer size actually provided.

PVD_CONFIG

This object stores the configuration information for the service provider associated with socket s. The exact format of this data structure is service provider specific.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	ws2spi.h

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