The TimeClient Sample Application

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The TimeClient sample application ("03 TimeClient.exe"), shown in Listing 3-2, tests the TimeService service. The source code and resource files for the application are in the 03-TimeClient directory on the companion CD. When you start the program, the dialog box in Figure 3-8 appears.

Figure 3-8. Initial dialog box in the TimeClient sample application

To see the client/server communication work, you must type the server name in the edit control at the top of the dialog box. If you are running the client and the server process on the same machine, type a period as the server name (as shown in Figure 3-8). When you click the Request Server's Time button, the client application calls CreateFile, which connects the client to the server, causing the server to wake up and process the client's request. If the server is not running, CreateFile fails and a message box similar to the one shown in Figure 3-9 appears.

Figure 3-9. Message box displayed by TimeClient when the TimeService service isn't running

If the service is up and running, CreateFile returns a valid handle, and the client waits for the time data to come across the pipe by placing a synchronous call to ReadFile. After the client has the data, the client's pipe handle is closed, the time from the server (which came across in universal time) is converted to the client's local time, and the initial dialog box is updated to look like Figure 3-10.

Figure 3-10. The updated dialog box for the TimeClient sample application

Listing 3-2. The TimeClient sample application

 
TimeClient.cpp
 /****************************************************************************** Module:  TimeClient.cpp Notices: Copyright (c) 2000 Jeffrey Richter ******************************************************************************/ #include "..\CmnHdr.h"                    // See Appendix A #include <WindowsX.h> #include "..\ClassLib\EnsureCleanup.h"    // See Appendix B #include "Resource.h" ////////////////////////////////////////////////////////////////////////////// BOOL Dlg_OnInitDialog(HWND hwnd, HWND hwndFocus, LPARAM lParam) {    chSETDLGICONS(hwnd, IDI_TIMECLIENT);    // Assume that the server is on the same machine as the client    SetDlgItemText(hwnd, IDC_SERVER, TEXT("."));    return(TRUE); } ////////////////////////////////////////////////////////////////////////////// void Dlg_OnCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify) {    switch (id) {    case IDCANCEL:       EndDialog(hwnd, id);        break;    case IDOK:       // Construct the pathname of the pipe       TCHAR sz[500];       sz[0] = sz[1] = TEXT(`\\');       GetDlgItemText(hwnd, IDC_SERVER, &sz[2], chDIMOF(sz) - 2);       lstrcat(sz, TEXT("\\pipe\\TimeService"));       // Attempt to connect to the pipe        // Get a handle to use to talk to the pipe       CEnsureCloseFile hpipe =           CreateFile(sz, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);       if (hpipe.IsValid()) {          // Valid handle, read time from pipe          SYSTEMTIME st;          DWORD cbRead = 0;          ReadFile(hpipe, &st, sizeof(st), &cbRead, NULL);          // Convert UTC time to client machine's local time and display it          SystemTimeToTzSpecificLocalTime(NULL, &st, &st);          GetDateFormat(LOCALE_USER_DEFAULT, DATE_LONGDATE, &st, NULL, sz,              chDIMOF(sz));          SetDlgItemText(hwnd, IDC_DATE, sz);          GetTimeFormat(LOCALE_USER_DEFAULT, LOCALE_NOUSEROVERRIDE, &st, NULL,              sz, chDIMOF(sz));          SetDlgItemText(hwnd, IDC_TIME, sz);       } else {          // Invalid handle, report an error          SetDlgItemText(hwnd, IDC_DATE, TEXT("Error"));          SetDlgItemText(hwnd, IDC_TIME, TEXT("Error"));          // Get the error code's textual description          HLOCAL hlocal = NULL;   // Buffer that gets the error message string          FormatMessageA(             FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER,             NULL, GetLastError(),              MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US), (PSTR) &hlocal,              0, NULL);          if (hlocal != NULL) {             chMB((PCSTR) LocalLock(hlocal));             LocalFree(hlocal);          }       }       break;    } } ////////////////////////////////////////////////////////////////////////////// INT_PTR WINAPI Dlg_Proc (HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {    switch (uMsg) {    chHANDLE_DLGMSG(hwnd, WM_INITDIALOG, Dlg_OnInitDialog);    chHANDLE_DLGMSG(hwnd, WM_COMMAND,    Dlg_OnCommand);    }    return(FALSE); } ////////////////////////////////////////////////////////////////////////////// int WINAPI _tWinMain(HINSTANCE hinstExe, HINSTANCE, PTSTR pszCmdLine, int) {    DialogBox(hinstExe, MAKEINTRESOURCE(IDD_TIMECLIENT), NULL, Dlg_Proc);    return(0); } //////////////////////////////// End Of File /////////////////////////////////