通过数据报套接字接收数据

在 Winsock 内核 (WSK) 应用程序将数据报套接字绑定到本地传输地址后，它可以通过该套接字接收数据报。 WSK 应用程序通过调用 WskReceiveFrom 函数通过数据报套接字接收数据报。

下面的代码示例演示 WSK 应用程序如何通过数据报套接字接收数据报。

// Prototype for the receive datagram IoCompletion routine
NTSTATUS
  ReceiveDatagramComplete(
    PDEVICE_OBJECT DeviceObject,
    PIRP Irp,
    PVOID Context
    );

// Function to receive a datagram
NTSTATUS
  ReceiveDatagram(
    PWSK_SOCKET Socket,
    PWSK_BUF DatagramBuffer
    )
{
  PWSK_PROVIDER_DATAGRAM_DISPATCH Dispatch;
  PIRP Irp;
  NTSTATUS Status;

  // Get pointer to the provider dispatch structure
  Dispatch =
    (PWSK_PROVIDER_DATAGRAM_DISPATCH)(Socket->Dispatch);

  // Allocate an IRP
  Irp =
    IoAllocateIrp(
      1,
      FALSE
      );

  // Check result
  if (!Irp)
  {
    // Return error
    return STATUS_INSUFFICIENT_RESOURCES;
  }

  // Set the completion routine for the IRP
  IoSetCompletionRoutine(
    Irp,
    ReceiveDatagramComplete,
    DatagramBuffer,  // Use the datagram buffer for the context
    TRUE,
    TRUE,
    TRUE
    );

  // Initiate the receive operation on the socket
  Status =
    Dispatch->WskReceiveFrom(
      Socket,
      DatagramBuffer,
      0,  // No flags are specified
      NULL,  // Not interested in the remote address
      NULL,  // Not interested in any associated control information
      NULL,
      NULL,
      Irp
      );

  // Return the status of the call to WskReceiveFrom()
  return Status;
}

// Receive datagram IoCompletion routine
NTSTATUS
  ReceiveDatagramComplete(
    PDEVICE_OBJECT DeviceObject,
    PIRP Irp,
    PVOID Context
    )
{
  UNREFERENCED_PARAMETER(DeviceObject);

  PWSK_BUF DataBuffer;
  ULONG ByteCount;

  // Check the result of the receive operation
  if (Irp->IoStatus.Status == STATUS_SUCCESS)
  {
    // Get the pointer to the data buffer
    DataBuffer = (PWSK_BUF)Context;
 
    // Get the number of bytes received
    ByteCount = (ULONG)(Irp->IoStatus.Information);

    // Process the received datagram
    ...
  }

  // Error status
  else
  {
    // Handle error
    ...
  }

  // Free the IRP
  IoFreeIrp(Irp);

  // Always return STATUS_MORE_PROCESSING_REQUIRED to
  // terminate the completion processing of the IRP.
  return STATUS_MORE_PROCESSING_REQUIRED;
}

作为调用 WskReceiveFrom 函数以通过数据报套接字接收每个数据报的替代方法，WSK 应用程序可以在套接字上启用 WskReceiveFromEvent 事件回调函数。 如果 WSK 应用程序在数据报套接字上启用 WskReceiveFromEvent 事件回调函数，则只要在套接字上收到新的数据报，WSK 子系统就会调用套接字的 WskReceiveFromEvent 事件回调函数。 有关启用数据报套接字的 WskReceiveFromEvent 事件回调函数的详细信息，请参阅 启用和禁用事件回调函数。

下面的代码示例演示 WSK 应用程序如何通过调用数据报套接字的 WskReceiveFromEvent 事件回调函数来接收 WSK 子系统的数据报。

// A datagram socket's WskReceiveFromEvent
// event callback function
NTSTATUS WSKAPI
  WskReceiveFromEvent(
    PVOID SocketContext,
    ULONG Flags,
    PWSK_DATAGRAM_INDICATION DataIndication
    )
{
  // Check for a valid data indication
  if (DataIndication != NULL)
  {
    // Loop through the list of data indication structures
    while (DataIndication != NULL)
    {
      // Process the data in the data indication structure
      ...

      // Move to the next data indication structure
      DataIndication = DataIndication->Next;
    }

    // Return status indicating the datagrams were received
    return STATUS_SUCCESS;
  }

  // Error
  else
  {
    // Close the socket
    ...

    // Return success since no datagrams were indicated
    return STATUS_SUCCESS;
  }
}

如果数据报套接字的 WskReceiveFromEvent 事件回调函数未从 DataIndication 参数指向的WSK_DATAGRAM_INDICATION结构列表中检索所有数据报，则它可以通过返回STATUS_PENDING来保留该列表以供进一步处理。 在这种情况下，WSK 应用程序必须调用 WskRelease 函数，以在完成从列表中的结构中检索所有数据报后，将WSK_DATAGRAM_INDICATION结构的列表释放回 WSK 子系统。