LPWSPENUMNETWORKEVENTS callback function (ws2spi.h)

Article
10/13/2021

The LPWSPEnumNetworkEvents function reports occurrences of network events for the indicated socket.

Syntax

LPWSPENUMNETWORKEVENTS Lpwspenumnetworkevents;

int Lpwspenumnetworkevents(
  [in]  SOCKET s,
  [in]  WSAEVENT hEventObject,
  [out] LPWSANETWORKEVENTS lpNetworkEvents,
  [out] LPINT lpErrno
)
{...}

Parameters

[in] s

Descriptor identifying the socket.

[in] hEventObject

Optional handle identifying an associated event object to be reset.

[out] lpNetworkEvents

Pointer to a WSANETWORKEVENTS structure that is filled with a record of occurred network events and any associated error codes. The WSANETWORKEVENTS structure is defined in the following text.

[out] lpErrno

Pointer to the error code.

Return value

The return value is zero if the operation was successful. Otherwise, the value SOCKET_ERROR is returned, and a specific error number is available in lpErrno.

Error Code	Meaning
WSAENETDOWN	The network subsystem has failed.
WSAEINVAL	Indicates that one of the specified parameters was invalid.
WSAEINPROGRESS	A blocking Windows Sockets call is in progress, or the service provider is still processing a callback function.
WSAENOTSOCK	The descriptor is not a socket.

Remarks

This function is used to report which network events have occurred for the indicated socket since the last invocation of this function. It is intended for use in conjunction with LPWSPEventSelect and LPWSPAsyncSelect, which associate an event object with one or more network events. Recording of network events commences when LPWSPEventSelect or LPWSPAsyncSelect is called with a nonzero lNetworkEvents argument, and remains in effect until another corresponding call is made to LPWSPEventSelect or LPWSPAsyncSelect with the lNetworkEvents argument set to zero.

LPWSPEnumNetworkEvents only reports network activity and errors nominated through LPWSPEventSelect. See the descriptions of LPWSPSelect and LPWSPAsyncSelect to find out how those functions report network activity and errors.

The socket's internal record of network events is copied to the structure referenced by lpNetworkEvents, whereafter the internal network events record is cleared. If hEventObject is non-null, the indicated event object is also reset. The Windows Sockets provider guarantees that the operations of copying the network event record, clearing it, and resetting any associated event object are atomic, such that the next occurrence of a nominated network event will cause the event object to become set. In the case of this function returning SOCKET_ERROR, the associated event object is not reset and the record of network events is not cleared.

The WSANETWORKEVENTS structure is defined on the WSANETWORKEVENTS reference page.

The lNetworkEvents member of the WSANETWORKEVENTS structure indicates which of the FD_XXX network events have occurred. The iErrorCode array is used to contain any associated error codes, with array index corresponding to the position of event bits in lNetworkEvents. The identifiers such as FD_READ_BIT and FD_WRITE_BIT can be used to index the iErrorCode array.

Note that only those elements of the iErrorCode array are set that correspond to the bits set in the lNetworkEvents member. Other members are not modified (this is important for backward compatibility with the Windows Socket 2 SPI clients that are not aware of new FD_ROUTING_INTERFACE_CHANGE and FD_ADDRESS_LIST_CHANGE events).

The following error codes can be returned along with the respective network event.

Event: FD_CONNECT

Error Code	Meaning
WSAEAFNOSUPPORT	Addresses in the specified family cannot be used with this socket.
WSAECONNREFUSED	An attempt to connect was forcefully rejected.
WSAENETUNREACH	The network cannot be reached from this host at this time.
WSAENOBUFS	No buffer space is available. The socket cannot be connected.
WSAETIMEDOUT	An attempt to connect timed out without establishing a connection.

Event: FD_CLOSE

Error Code	Meaning
WSAENETDOWN	The network subsystem has failed.
WSAECONNRESET	The connection was reset by the remote side.
WSAECONNABORTED	The connection was terminated due to a time-out or other failure.

Event: FD_READ, FD_WRITE, FD_OOB, FD_ACCEPT, FD_QOS, FD_GROUP_QOS, FD_ADDRESS_LIST_CHANGE

Error Code	Meaning
WSAENETDOWN	The network subsystem has failed.

Event: FD_ROUTING_INTERFACE_CHANGE

Error Code	Meaning
WSAENETUNREACH	The specified destination is no longer reachable.
WSAENETDOWN	The network subsystem has failed.

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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