用于MetaTrader 5的WebSocket：借助Windows API实现异步客户端连接（基础篇）

class=class="str">"cmt">// Set hSession
hSession = WinHttpOpen(L"MyApp", WINHTTP_ACCESS_TYPE_NO_PROXY, WINHTTP_NO_PROXY_NAME, WINHTTP_NO_PROXY_BYPASS, WINHTTP_FLAG_ASYNC);
if (hSession == NULL)
      ErrorCode = ERROR_INVALID_HANDLE;
class=class="str">"cmt">// Return error code
class="kw">return ErrorCode;
if (!WinHttpSetOption(hWebSocket, WINHTTP_OPTION_CONTEXT_VALUE, (LPVOID)this, class="kw">sizeof(this)))
{
      class=class="str">"cmt">// Handle error
      ErrorCode = GetLastError();
      class="kw">return ErrorCode;
}
if (WinHttpSetStatusCallback(hWebSocket, WebSocketCallback, WINHTTP_CALLBACK_FLAG_ALL_COMPLETIONS, class="num">0) == WINHTTP_INVALID_STATUS_CALLBACK)
{
      ErrorCode = GetLastError();
      class="kw">return ErrorCode;
}
class="type">void WebSocketCallback(HINTERNET hInternet, DWORD_PTR dwContext, DWORD dwInternetStatus, LPVOID lpvStatusInformation, DWORD dwStatusInformationLength)

class WebSocketClient {
class="kw">private:
    HINTERNET hSession;
    HINTERNET hConnect;
    HINTERNET hRequest;
    HINTERNET hWebSocket;
    DWORD initialized;
    DWORD bytesTX;
    DWORD ErrorCode;
    DWORD completed_websocket_operation;

class=class="str">"cmt">//internal queue of frames sent from a server
std::queue<Frame>* frames;
class=class="str">"cmt">//client state;
ENUM_WEBSOCKET_STATE status;
class=class="str">"cmt">//sets an hSession handle
DWORD Initialize(VOID);
class=class="str">"cmt">// reset state of object
class=class="str">"cmt">/*
 reset_error: boolean flag indicating whether to rest the
 internal error buffers.
*/
VOID  Reset(class="type">bool reset_error = true);

class="kw">public:
class=class="str">"cmt">//constructor(s)
WebSocketClient(VOID);
WebSocketClient(const WebSocketClient&) = class="kw">delete;
WebSocketClient(WebSocketClient&&) = class="kw">delete;
WebSocketClient& class="kw">operator=(const WebSocketClient&) = class="kw">delete;
WebSocketClient& class="kw">operator=(WebSocketClient&&) = class="kw">delete;
class=class="str">"cmt">//destructor
~WebSocketClient(VOID);
class=class="str">"cmt">//received bytes;
DWORD bytesRX;
class=class="str">"cmt">// receive buffer
std::vector<BYTE> rxBuffer;
class=class="str">"cmt">// received frame type;
WINHTTP_WEB_SOCKET_BUFFER_TYPE rxBufferType;
class=class="str">"cmt">// Get the winhttp websocket handle
class=class="str">"cmt">/*
class="kw">return: returns the hWebSocket handle which is used to
identify a websocket connection instance
*/
HINTERNET WebSocketHandle(VOID);
class=class="str">"cmt">// Connect to a server
class=class="str">"cmt">/*
  hsession: HINTERNET session handle
  host: is the url
  port: prefered port number to use
  secure: class="num">0 is false, non-zero is true
  class="kw">return: DWORD error code, class="num">0 indicates success
  and non-zero for failure
*/
DWORD Connect(const WCHAR* host, const INTERNET_PORT port, const DWORD secure);

class=class="str">"cmt">// Send data to the WebSocket server
class=class="str">"cmt">/*
   bufferType: WINHTTP_WEB_SOCKET_BUFFER_TYPE enumeration of the frame type
   pBuffer: pointer to the data to be sent
   dwLength: size of pBuffer data
   class="kw">return: DWORD error code, class="num">0 indicates success
   and non-zero for failure
*/
DWORD Send(WINHTTP_WEB_SOCKET_BUFFER_TYPE bufferType, class="type">void* pBuffer, DWORD dwLength);
class=class="str">"cmt">// Close the connection to the server
class=class="str">"cmt">/*
   status: WINHTTP_WEB_SOCKET_CLOSE_STATUS enumeration of the close notification to be sent
   reason: character class="type">class="kw">string of extra data sent with the close notification
   class="kw">return: DWORD error code, class="num">0 indicates success
   and non-zero for failure
*/

DWORD Close(WINHTTP_WEB_SOCKET_CLOSE_STATUS status, CHAR* reason = NULL);
class=class="str">"cmt">// Retrieve the close status sent by a server
class=class="str">"cmt">/*
 pusStatus: pointer to a close status code that will be filled upon class="kw">return.
 pvReason: pointer to a buffer that will receive a close reason
 dwReasonLength: The length of the pvReason buffer,
 pdwReasonLengthConsumed:The number of bytes consumed. If pvReason is NULL and dwReasonLength is class="num">0,
pdwReasonLengthConsumed will contain the size of the buffer that needs to be allocated
 by the calling application.
 class="kw">return: DWORD error code, class="num">0 indicates success
 and non-zero for failure
*/
DWORD QueryCloseStatus(USHORT* pusStatus, PVOID pvReason, DWORD dwReasonLength, DWORD* pdwReasonLengthConsumed);
class=class="str">"cmt">// read from the server
class=class="str">"cmt">/*
 bufferType: WINHTTP_WEB_SOCKET_BUFFER_TYPE enumeration of the frame type
 pBuffer: pointer to the data to be sent
 pLength: size of pBuffer
 bytesRead: pointer to number bytes read from the server
 pBufferType: pointer to type of frame sent from the server
 class="kw">return: DWORD error code, class="num">0 indicates success
 and non-zero for failure
*/
DWORD Receive(PVOID pBuffer, DWORD pLength, DWORD* bytesRead, WINHTTP_WEB_SOCKET_BUFFER_TYPE* pBufferType);
class=class="str">"cmt">// Check client state
class=class="str">"cmt">/*
 class="kw">return: ENUM_WEBSOCKET_STATE enumeration
*/
ENUM_WEBSOCKET_STATE Status(VOID);
class=class="str">"cmt">// get frames cached in the internal queue
class=class="str">"cmt">/*
 pBuffer: User supplied container to which data is written to
 pLength: size of pBuffer
 pBufferType: WINHTTP_WEB_SOCKET_BUFFER_TYPE enumeration of frame type
*/
VOID Read(BYTE* pBuffer, DWORD pLength, WINHTTP_WEB_SOCKET_BUFFER_TYPE* pBufferType);
class=class="str">"cmt">// get bytes received
class=class="str">"cmt">/*
 class="kw">return: Size of most recently cached frame sent from a server
*/
DWORD ReadAvailable(VOID);
class=class="str">"cmt">// get the last error
class=class="str">"cmt">/*
 class="kw">return: returns the last error code
*/
DWORD LastError(VOID);
class=class="str">"cmt">// activate callback function
class=class="str">"cmt">/*
 class="kw">return: DWORD error code, class="num">0 indicates success
 and non-zero for failure
*/
DWORD EnableCallBack(VOID);
class=class="str">"cmt">// set error 
class=class="str">"cmt">/*
 message: Error description to be captured
 errorcode: new user defined error code
*/
VOID SetError(const DWORD errorcode);
class=class="str">"cmt">// get the last completed operation
class=class="str">"cmt">/*
returns: DWORD constant of last websocket operation
*/