WSAEnumNetworkEvents

The Windows Sockets WSAEnumNetworkEvents function discovers occurrences of network events for the indicated socket, clear internal network event records, and reset event objects (optional).

int WSAEnumNetworkEvents (
  SOCKET s,                           
  WSAEVENT hEventObject,              
  LPWSANETWORKEVENTS lpNetworkEvents  
);

Parameters

s: [in] A descriptor identifying the socket.
hEventObject: [in] An optional handle identifying an associated event object to be reset.
lpNetworkEvents: [out] A pointer to a WSANETWORKEVENTS structure that is filled with a record of network events that occurred and any associated error codes.

Remarks

The WSAEnumNetworkEvents function is used to discover which network events have occurred for the indicated socket since the last invocation of this function. It is intended for use in conjunction with WSAEventSelect, which associates an event object with one or more network events. The recording of network events commences when WSAEventSelect is called with a nonzero lNetworkEvents parameter and remains in effect until another call is made to WSAEventSelect with the lNetworkEvents parameter set to zero, or until a call is made to WSAAsyncSelect.

WSAEnumNetworkEvents only reports network activity and errors nominated through WSAEventSelect. See the descriptions of select and WSAAsyncSelect 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 the hEventObject parameter is not 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 automatic, 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 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 the array index corresponding to the position of event bits in lNetworkEvents. 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 lNetworkEvents field. Other fields are not modified (this is important for backwards compatibility with the applications 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 corresponding network event:

Event: FD_CONNECT

Error Code	Meaning
WSAEAFNOSUPPORT	Addresses in the specified family cannot be used with this socket.
WSAECONNREFUSED	The 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	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

Event: FD_WRITE

Event: FD_OOB

Event: FD_ACCEPT

Event: FD_QOS

Event: FD_GROUP_QOS

Event: 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.

Return Values

The return value is zero if the operation was successful. Otherwise, the value SOCKET_ERROR is returned, and a specific error number can be retrieved by calling WSAGetLastError.

Error Codes

WSANOTINITIALISED	A successful WSAStartup must occur before using this function.
WSAENETDOWN	The network subsystem has failed.
WSAEINVAL	Indicates that one of the specified parameters was invalid.
WSAEINPROGRESS	A blocking Windows Sockets 1.1 call is in progress, or the service provider is still processing a callback function.
WSAENOTSOCK	The descriptor is not a socket.
WSAEFAULT	The lpNetworkEvents argument is not a valid part of the user address space.

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