WSPAccept (Compact 2013)

3/26/2014

This function conditionally accepts a connection based on the return value of a condition function.

Syntax

SOCKET WSPAccept(
  SOCKET s,
  struct sockaddr FAR* addr,
  LPINT addrlen,
  LPCONDITIONPROC lpfnCondition,
  DWORD dwCallbackData,
  LPINT lpErrno 
);

Parameters

• s
  [in] Descriptor identifying a socket that is listening for connections after a WSPListen.

• addr
  [out] Optional pointer to a buffer that receives the address of the connecting entity, as known to the service provider. The exact format of the addr parameter is determined by the address family established when the socket was created.

• addrlen
  [in, out] Optional pointer to an integer that contains the length of the addr parameter.

• lpfnCondition
  [in] Procedure instance address of an optional-condition function furnished by Windows Sockets. This function is used in the accept or reject decision based on the caller information passed in as parameters.

• dwCallbackData
  [in] Callback data to be passed back to the Winsock client as the value of the dwCallbackData parameter of the condition function. This parameter is not interpreted by the service provider.

• lpErrno
  [out] Pointer to the error code.

Return Value

If no error occurs, this function returns a value of type SOCKET that is a descriptor for the accepted socket. Otherwise, a value of INVALID_SOCKET is returned, and a specific error code is available in lpErrno.

The following table shows the possible error codes.

Remarks

This function extracts the first connection on the queue of pending connections on socket s, and checks it against the condition function, provided the condition function is specified (that is, not NULL). The condition function must be executed in the same thread as this routine. If the condition function returns CF_ACCEPT, this function creates a new socket.

Newly created sockets have the same properties as the socket s, including network events registered with WSPEventSelect. When new socket descriptors are allocated, non-IFS providers must call WPUCreateSocketHandle.

If the condition function returns CF_REJECT, WSPAccept rejects the connection request. If the application's accept/reject decision cannot be made immediately, the condition function will return CF_DEFER to indicate that no decision has been made. No action about this connection request is to be taken by the service provider. When the application is ready to take action on the connection request, it will invoke WSPAccept again and return either CF_ACCEPT or CF_REJECT as a return value from the condition function.

For sockets that are in the (default) blocking mode, if no pending connections are present on the queue, WSPAccept blocks the caller until a connection is present. For sockets in nonblocking mode, if this function is called when no pending connections are present on the queue, WSPAccept returns the error code WSAEWOULDBLOCK. The accepted socket cannot be used to accept more connections. The original socket remains open.

The parameter addr is a result parameter that is filled with the address of the connecting entity, as known to the service provider. The exact format of the addr parameter is determined by the address family in which the communication is occurring. The addrlen is a value-result parameter; it will initially contain the amount of space pointed to by addr. On return, it must contain the actual length (in bytes) of the address returned by the service provider. This call is used with connection-oriented socket types such as SOCK_STREAM. If addr and/or addrlen are equal to NULL, then no information about the remote address of the accepted socket is returned. Otherwise, these two parameters shall be filled in regardless of whether the condition function is specified or what it returns.

The following code sample shows the prototype of the condition function.

int CALLBACK 
ConditionFunc(
  IN LPWSABUF lpCallerId, 
  IN LPWSABUF lpCallerData, 
  IN OUT LPQOS lpSQOS, 
  IN OUT LPQOS lpGQOS,
  IN LPWSABUF lpCalleeId, 
  IN LPWSABUF lpCalleeData, 
  OUT GROUP FAR* g, 
  IN DWORD  dwCallbackData 
);

The lpCallerId and lpCallerData are value parameters that must contain the address of the connecting entity and any user data that was sent along with the connection request. If no caller identifier or caller data is available, the corresponding parameter will be NULL. Many network protocols do not support connect-time caller data. Most conventional network protocols can be expected to support caller identifier information at connection-request time. The buf part of the WSABUF pointed to by lpCallerId points to a sockaddr. The sockaddr is interpreted according to its address family (typically by casting the sockaddr to some type specific to the address family).

The lpCalleeId is a value parameter that contains the local address of the connected entity. The buf part of the WSABUF pointed to by lpCalleeId points to a sockaddr. The sockaddr is interpreted according to its address family (typically by casting the sockaddr to some type specific to the address family).

The lpCalleeData is a result parameter used by the condition function to supply user data back to the connecting entity. The storage for this data must be provided by the service provider. The lpCalleeData->len initially contains the length of the buffer allocated by the service provider and pointed to by lpCalleeData->buf. A value of zero means passing user data back to the caller is not supported. The condition function will copy up to lpCalleeData->len bytes of data into lpCalleeData->buf, and then update lpCalleeData->len to indicate the actual number of bytes transferred. If no user data is to be passed back to the caller, the condition function will set lpCalleeData->len to zero. The format of all address and user data is specific to the address family to which the socket belongs.

The dwCallbackData parameter value passed to the condition function is the value passed as the dwCallbackData parameter in the original WSPAccept call. This value is interpreted only by the Winsock client. This allows a client to pass some context information from the WSPAccept call site through to the condition function, which provides the condition function with any additional information required to determine whether to accept the connection. A typical usage is to pass a (suitably cast) pointer to a data structure containing references to application-defined objects with which this socket is associated.

Requirements

See Also

Reference

Winsock SPI Functions
WSPBind
WSPConnect
WSPGetSockOpt
WSPListen
WSPSelect
WSPSocket
WSPEventSelect