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Get POP3 GMail OAuth2 Access Token for Desktop App

See more GMail SMTP/IMAP/POP Examples

Demonstrates how to get a POP3 GMail OAuth2 access token from a desktop application or script.

This example requires a browser window to be displayed to allow the GMail account owner to authorize the access. The code for displaying the web browser is omitted. Suggestions for a few programming languages are provided in code comments. To complete this example, you will need to find out how to display a web browser and navigate to the URL returned by the call to oauth2.StartAuth.

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Local $bSuccess = False

; This example requires the Chilkat API to have been previously unlocked.
; See Global Unlock Sample for sample code.

$oOauth2 = ObjCreate("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.
$oOauth2.ListenPort = 55568

$oOauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth"
$oOauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

; Replace these with actual values.
$oOauth2.ClientId = "GOOGLE-CLIENT-ID"
$oOauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

$oOauth2.CodeChallenge = True
$oOauth2.CodeChallengeMethod = "S256"

; See https://developers.google.com/gmail/api/auth/scopes for a list of GMail scopes.
; This is the full-permissions scope for GMail, which is sufficient for all POP3 operations to pop.gmail.com
$oOauth2.Scope = "https://mail.google.com/"

; Important note about GMail scope for sending email:
; If the SMTP protocol is used for sending, then the full GMail scope is required: "https://mail.google.com/"
; Here is an example that sends GMail via the SMTP protocol:  Send GMail using SMTP
; If the GMail REST API is used, then the more restrictive Gmail scope can be used:  "https://www.googleapis.com/auth/gmail.send"
; Here is an example that sends GMail using the GMail REST API: Send GMail using REST API

; Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
Local $sUrl = $oOauth2.StartAuth()
If ($oOauth2.LastMethodSuccess = False) Then
    ConsoleWrite($oOauth2.LastErrorText & @CRLF)
    Exit
EndIf

; Launch the system's default browser navigated to the URL.
$bSuccess = $oOauth2.LaunchBrowser($sUrl)
If ($bSuccess = False) Then
    ConsoleWrite($oOauth2.LastErrorText & @CRLF)
    Exit
EndIf

; Now wait for the authorization.
; We'll wait for a max of 30 seconds.
Local $iNumMsWaited = 0
While ($iNumMsWaited < 30000) And ($oOauth2.AuthFlowState < 3)
    $oOauth2.SleepMs 100
    $iNumMsWaited = $iNumMsWaited + 100
Wend

; If there was no response from the browser within 30 seconds, then 
; the AuthFlowState will be equal to 1 or 2.
; 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
; 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
; In that case, cancel the background task started in the call to StartAuth.
If ($oOauth2.AuthFlowState < 3) Then
    $oOauth2.Cancel()
    ConsoleWrite("No response from the browser!" & @CRLF)
    Exit
EndIf

; Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
; The possible AuthFlowState values are:
; 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
; 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
; 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
If ($oOauth2.AuthFlowState = 5) Then
    ConsoleWrite("OAuth2 failed to complete." & @CRLF)
    ConsoleWrite($oOauth2.FailureInfo & @CRLF)
    Exit
EndIf

If ($oOauth2.AuthFlowState = 4) Then
    ConsoleWrite("OAuth2 authorization was denied." & @CRLF)
    ConsoleWrite($oOauth2.AccessTokenResponse & @CRLF)
    Exit
EndIf

If ($oOauth2.AuthFlowState <> 3) Then
    ConsoleWrite("Unexpected AuthFlowState:" & $oOauth2.AuthFlowState & @CRLF)
    Exit
EndIf

; Save the full JSON access token response to a file.
$oSbJson = ObjCreate("Chilkat.StringBuilder")
$oSbJson.Append($oOauth2.AccessTokenResponse)
$oSbJson.WriteFile("qa_data/tokens/gmail_pop3.json","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"
; 	}
; 
ConsoleWrite("OAuth2 authorization granted!" & @CRLF)
ConsoleWrite("Access Token = " & $oOauth2.AccessToken & @CRLF)