(Unicode C) Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

Note: This example requires Chilkat v10.1.2 or greater.

Chilkat C/C++ Library Downloads
MS Visual C/C++ C++ Builder Linux C/C++ Alpine Linux C/C++	MacOS C/C++ iOS C/C++ Android C/C++ MinGW C/C++

#include <C_CkOAuth2W.h>
#include <C_CkStringBuilderW.h>

void ChilkatSample(void)
    {
    HCkOAuth2W oauth2;
    const wchar_t *url;
    BOOL success;
    int numMsWaited;
    HCkStringBuilderW sbJson;

    // To further clarify, see OAuth 2.0 Authorization Flow

    oauth2 = CkOAuth2W_Create();

    // For Google OAuth2, set the listen port equal to the port used
    // in the Authorized Redirect URL for the Client ID.
    // For example, in this case the Authorized Redirect URL would be http://localhost:55568/
    // Your app should choose a port not likely not used by any other application.
    CkOAuth2W_putListenPort(oauth2,55568);

    CkOAuth2W_putAuthorizationEndpoint(oauth2,L"https://accounts.google.com/o/oauth2/v2/auth");
    CkOAuth2W_putTokenEndpoint(oauth2,L"https://www.googleapis.com/oauth2/v4/token");

    // Replace these with actual values.
    CkOAuth2W_putClientId(oauth2,L"GOOGLE-CLIENT-ID");
    CkOAuth2W_putClientSecret(oauth2,L"GOOGLE-CLIENT-SECRET");

    // To use Gmail's OAuth2 for sending emails via the SMTP protocol, you need to request the https://mail.google.com/ scope. 
    // See About GMail SMTP OAuth2 Scopes
    CkOAuth2W_putScope(oauth2,L"https://mail.google.com/");

    // Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
    url = CkOAuth2W_startAuth(oauth2);
    if (CkOAuth2W_getLastMethodSuccess(oauth2) != TRUE) {
        wprintf(L"%s\n",CkOAuth2W_lastErrorText(oauth2));
        CkOAuth2W_Dispose(oauth2);
        return;
    }

    // Launch the default browser on the system and navigate to the url.
    // The LaunchBrowser method was added in Chilkat v10.1.2.
    success = CkOAuth2W_LaunchBrowser(oauth2,url);
    if (success == FALSE) {
        wprintf(L"%s\n",CkOAuth2W_lastErrorText(oauth2));
        CkOAuth2W_Dispose(oauth2);
        return;
    }

    // Wait for the user to approve or deny authorization in the browser.
    numMsWaited = 0;
    while ((numMsWaited < 90000) && (CkOAuth2W_getAuthFlowState(oauth2) < 3)) {
        CkOAuth2W_SleepMs(oauth2,100);
        numMsWaited = numMsWaited + 100;
    }

    // If the browser does not respond within the specified time, AuthFlowState will be:
    // 
    // 1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
    // 2: Waiting for Final Response – The thread is awaiting the final access token response.
    // In either case, cancel the background task initiated by StartAuth.

    if (CkOAuth2W_getAuthFlowState(oauth2) < 3) {
        CkOAuth2W_Cancel(oauth2);
        wprintf(L"No response from the browser!\n");
        CkOAuth2W_Dispose(oauth2);
        return;
    }

    // Check AuthFlowState to determine if authorization was granted, denied, or failed:
    // 
    // 3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
    // 4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
    // 5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

    if (CkOAuth2W_getAuthFlowState(oauth2) == 5) {
        wprintf(L"OAuth2 failed to complete.\n");
        wprintf(L"%s\n",CkOAuth2W_failureInfo(oauth2));
        CkOAuth2W_Dispose(oauth2);
        return;
    }

    if (CkOAuth2W_getAuthFlowState(oauth2) == 4) {
        wprintf(L"OAuth2 authorization was denied.\n");
        wprintf(L"%s\n",CkOAuth2W_accessTokenResponse(oauth2));
        CkOAuth2W_Dispose(oauth2);
        return;
    }

    if (CkOAuth2W_getAuthFlowState(oauth2) != 3) {
        wprintf(L"Unexpected AuthFlowState:%d\n",CkOAuth2W_getAuthFlowState(oauth2));
        CkOAuth2W_Dispose(oauth2);
        return;
    }

    // Save the full JSON access token response to a file.
    sbJson = CkStringBuilderW_Create();
    CkStringBuilderW_Append(sbJson,CkOAuth2W_accessTokenResponse(oauth2));
    CkStringBuilderW_WriteFile(sbJson,L"qa_data/tokens/_gmailSmtp.json",L"utf-8",FALSE);

    // The saved JSON response looks like this:

    // 	{
    // 	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtBBBHkZzrwlARkwX6R3O0PCDEzRlfaQ",
    // 	 "token_type": "Bearer",
    // 	 "expires_in": 3600,
    // 	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
    // 	}
    // 
    wprintf(L"OAuth2 authorization granted!\n");
    wprintf(L"Access Token = %s\n",CkOAuth2W_accessToken(oauth2));


    CkOAuth2W_Dispose(oauth2);
    CkStringBuilderW_Dispose(sbJson);

    }