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Lấy con trỏ vào hộp danh sách được sử dụng cho các thông báo trạng thái Lập trình với Thư viện Class WinSockdữ liệu khối trong hàng đợi / / nên không bao giờ xảy ra nhưng chắc chắn rằng bộ nhớ được giải phóng chỉ trong trường hợp pDataRead | 06 Part IV Programming with the WinSock Class Library Listing 15.6. continued get pointer to list box used for status messages CListBox plb CListBox GetDlgItem IDC_LIST_STATUS switch wParam case CWINSOCK_DONE_WRITING lParam pointer to data that was sent pDataWritten LPVOID lParam wsprintf pszMessage Heartbeat sent plb- InsertString 0 pszMessage m_pszHeartbeat 0 same as pDataWritten 0 break case CWINSOCK_ERROR_WRITING lParam pointer to data that generated error sending pDataWritten LPVOID lParam wsprintf pszMessage Error sending heartbeat plb- InsertString 0 pszMessage m_pszHeartbeat 0 same as pDataWritten 0 break case CWINSOCK_DONE_READING lParam data chunks in gueue should never happen but make sure the memory is freed just in case pDataRead m_pDatagram- Read nLen free pDataRead break case CWINSOCK_ERROR_READING break default break return 0L CServerView OnTimer Sends periodic heartbeats to the connected client through the datagram. void CServerView OnTimer UINT nIDEvent char pszMessage 1000 informational message ifdef HEARTBEAT_TEST static int nHeartbeatTest 0 nHeartbeatTest if nHeartbeatTest 10 ỊỊ nHeartbeatTest 11 ỊỊ nHeartbeatTest 20 ỊỊ nHeartbeatTest 21 return endif Chapter 15 Practical Client Server Database Application make sure we are not sending out of a bad datagram socket if m_pDatagram NULL return get pointer to list box used for status messages CLiStBox plb CListBox GetDlgItem IDC_LIST_STATUS send the buffer unless the previous send hasn t completed yet if m_pszHeartbeat 0 lstrcpy m_pszHeartbeat HEARTBEAT_STRING be sure to send terminating NULL character if m_pDatagram- Write lstrlen m_pszHeartbeat 1 m_pszHeartbeat m_sinClient CWInSock_NOeRroR m_pszHeartbeat 0 wsprintf pszMessage Error sending heartbeat plb- InsertString 0 pszMessage CFormView OnTimer nIDEvent Figures 15.1 and 15.2 show the client and server in action. FIGURE 15.1. The client INICLNT Summary This chapter demonstrates the use of the CWinSock CDatagramSocket and CStreamSocket objects. It
