Dart Requires Chilkat v10.1.2+

Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

This example show how to obtain a Gmail SMTP OAuth2 access token from a desktop application or script, enabling the use of XOAUTH2 authentication. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // To further clarify, see OAuth 2.0 Authorization Flow

  final oauth2 = CkOAuth2();

  // 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.
  oauth2.listenPort = 55568;

  oauth2.authorizationEndpoint = 'https://accounts.google.com/o/oauth2/v2/auth';
  oauth2.tokenEndpoint = 'https://www.googleapis.com/oauth2/v4/token';

  // Replace these with actual values.
  oauth2.clientId = 'GOOGLE-CLIENT-ID';
  oauth2.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
  oauth2.scope = 'https://mail.google.com/';

  // Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
  final String url;
  try {
    url = oauth2.startAuth();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Launch the default browser on the system and navigate to the url.
  // The LaunchBrowser method was added in Chilkat v10.1.2.
  try {
    oauth2.launchBrowser(url);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Wait for the user to approve or deny authorization in the browser.
  var numMsWaited = 0;
  while ((numMsWaited < 90000) && (oauth2.authFlowState < 3)) {
    oauth2.sleepMs(100);
    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 (oauth2.authFlowState < 3) {
    oauth2.cancel();
    print('No response from the browser!');
    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 (oauth2.authFlowState == 5) {
    print('OAuth2 failed to complete.');
    print(oauth2.failureInfo);
    return;
  }

  if (oauth2.authFlowState == 4) {
    print('OAuth2 authorization was denied.');
    print(oauth2.accessTokenResponse);
    return;
  }

  if (oauth2.authFlowState != 3) {
    print('Unexpected AuthFlowState:${oauth2.authFlowState}');
    return;
  }

  // Save the full JSON access token response to a file.
  final sbJson = CkStringBuilder();
  sbJson.append(oauth2.accessTokenResponse);
  sbJson.writeFile('qa_data/tokens/_gmailSmtp.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"
  // 	}
  // 
  print('OAuth2 authorization granted!');
  print('Access Token = ${oauth2.accessToken}');
}