(Visual FoxPro) Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loOauth2
LOCAL lcUrl
LOCAL lnSuccess
LOCAL lnNumMsWaited
LOCAL loSbJson

* To further clarify, see OAuth 2.0 Authorization Flow

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.OAuth2')
loOauth2 = CreateObject('Chilkat.OAuth2')

* 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.
loOauth2.ListenPort = 55568

loOauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth"
loOauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

* Replace these with actual values.
loOauth2.ClientId = "GOOGLE-CLIENT-ID"
loOauth2.ClientSecret = "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
loOauth2.Scope = "https://mail.google.com/"

* Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
lcUrl = loOauth2.StartAuth()
IF (loOauth2.LastMethodSuccess <> 1) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* Launch the default browser on the system and navigate to the url.
* The LaunchBrowser method was added in Chilkat v10.1.2.
lnSuccess = loOauth2.LaunchBrowser(lcUrl)
IF (lnSuccess = 0) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* Wait for the user to approve or deny authorization in the browser.
lnNumMsWaited = 0
DO WHILE (lnNumMsWaited < 90000) AND (loOauth2.AuthFlowState < 3)
    loOauth2.SleepMs(100)
    lnNumMsWaited = lnNumMsWaited + 100
ENDDO

* 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 (loOauth2.AuthFlowState < 3) THEN
    loOauth2.Cancel()
    ? "No response from the browser!"
    RELEASE loOauth2
    CANCEL
ENDIF

* 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 (loOauth2.AuthFlowState = 5) THEN
    ? "OAuth2 failed to complete."
    ? loOauth2.FailureInfo
    RELEASE loOauth2
    CANCEL
ENDIF

IF (loOauth2.AuthFlowState = 4) THEN
    ? "OAuth2 authorization was denied."
    ? loOauth2.AccessTokenResponse
    RELEASE loOauth2
    CANCEL
ENDIF

IF (loOauth2.AuthFlowState <> 3) THEN
    ? "Unexpected AuthFlowState:" + STR(loOauth2.AuthFlowState)
    RELEASE loOauth2
    CANCEL
ENDIF

* Save the full JSON access token response to a file.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbJson = CreateObject('Chilkat.StringBuilder')
loSbJson.Append(loOauth2.AccessTokenResponse)
loSbJson.WriteFile("qa_data/tokens/_gmailSmtp.json","utf-8",0)

* 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"
* 	}
* 
? "OAuth2 authorization granted!"
? "Access Token = " + loOauth2.AccessToken

RELEASE loOauth2
RELEASE loSbJson