PowerBuilder

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.

PowerBuilder

integer li_rc
long li_Success
oleobject loo_Oauth2
string ls_Url
long li_NumMsWaited
oleobject loo_SbJson

li_Success = 0

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

loo_Oauth2 = create oleobject
li_rc = loo_Oauth2.ConnectToNewObject("Chilkat.OAuth2")
if li_rc < 0 then
    destroy loo_Oauth2
    MessageBox("Error","Connecting to COM object failed")
    return
end if

//  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.
loo_Oauth2.ListenPort = 55568

loo_Oauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth"
loo_Oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

//  Replace these with actual values.
loo_Oauth2.ClientId = "GOOGLE-CLIENT-ID"
loo_Oauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

loo_Oauth2.CodeChallenge = 1
loo_Oauth2.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
loo_Oauth2.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.
ls_Url = loo_Oauth2.StartAuth()
if loo_Oauth2.LastMethodSuccess = 0 then
    Write-Debug loo_Oauth2.LastErrorText
    destroy loo_Oauth2
    return
end if

//  Launch the system's default browser navigated to the URL.
li_Success = loo_Oauth2.LaunchBrowser(ls_Url)
if li_Success = 0 then
    Write-Debug loo_Oauth2.LastErrorText
    destroy loo_Oauth2
    return
end if

//  Now wait for the authorization.
//  We'll wait for a max of 30 seconds.
li_NumMsWaited = 0
do while (li_NumMsWaited < 30000) AND (loo_Oauth2.AuthFlowState < 3)
    loo_Oauth2.SleepMs(100)
    li_NumMsWaited = li_NumMsWaited + 100
loop

//  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 loo_Oauth2.AuthFlowState < 3 then
    loo_Oauth2.Cancel()
    Write-Debug "No response from the browser!"
    destroy loo_Oauth2
    return
end if

//  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 loo_Oauth2.AuthFlowState = 5 then
    Write-Debug "OAuth2 failed to complete."
    Write-Debug loo_Oauth2.FailureInfo
    destroy loo_Oauth2
    return
end if

if loo_Oauth2.AuthFlowState = 4 then
    Write-Debug "OAuth2 authorization was denied."
    Write-Debug loo_Oauth2.AccessTokenResponse
    destroy loo_Oauth2
    return
end if

if loo_Oauth2.AuthFlowState <> 3 then
    Write-Debug "Unexpected AuthFlowState:" + string(loo_Oauth2.AuthFlowState)
    destroy loo_Oauth2
    return
end if

//  Save the full JSON access token response to a file.
loo_SbJson = create oleobject
li_rc = loo_SbJson.ConnectToNewObject("Chilkat.StringBuilder")

loo_SbJson.Append(loo_Oauth2.AccessTokenResponse)
loo_SbJson.WriteFile("qa_data/tokens/gmail_pop3.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"
//  	}
//  
Write-Debug "OAuth2 authorization granted!"
Write-Debug "Access Token = " + loo_Oauth2.AccessToken


destroy loo_Oauth2
destroy loo_SbJson