Google FCM HTTP v1 Delphi

Google FCM Delphi Client

Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets you reliably send messages at no cost.

Using FCM, you can notify a client app that new email or other data is available to sync. You can send notification messages to drive user re-engagement and retention. For use cases such as instant messaging, a message can transfer a payload of up to 4096 bytes to a client app.

The component supports the HTTP v1 API.

Google FCM component client can login to Google Servers using the following methods:

• gcaOAuth2: OAuth2 protocol
• gcaJWT: JWT tokens.

OAuth2

The login is done using a webbrowser where the user logins with his own user and authorizes the FCM requests.

• GoogleCloudOptions.OAuth2.ClientId: is the ClientID provided by Google to Authenticate through OAuth2 protocol.
• GoogleCloudOptions.OAuth2.ClientSecret: is the Client Secret string provided by Google to Authenticate through OAuth2 protocol.
• GoogleCloudOptions.OAuth2.Scope: is the scope of OAuth2, usually there is no need to modify the default value unless you need to get more access than default.
• GoogleCloudOptions.OAuth2.LocalIP: OAuth2 protocol requires a server listening answer from Authentication server, this is the IP or DNS. By default is 127.0.0.1.
• GoogleCloudOptions.OAuth2.LocalPort: Local server listening port.
• GoogleCloudOptions.OAuth2.RedirectURL: if you need to set a redirect url different from LocalPort + LocalIP, you can set in this property (example: http://127.0.0.1:8080/oauth2).

Service Accounts

The login is done signing the requests using a private key provided by google, these method is recommended for automated services or applications without user interaction.

• GoogleCloudOptions.JWT.ClientEmail: is the Client Email name provided creating the new service account. "client_email" node in the JSON configuration file.
• GoogleCloudOptions.JWT.Subject: is the Client Email name provided creating the new service account. "client_email" node in the JSON configuration file.
• GoogleCloudOptions.JWT.PrivateKeyId: is the Private Key Id provided by google. "private_key_id" node in the JSON configuration file.
• GoogleCloudOptions.JWT.PrivateKey: is the Private Key certificate provided by google. "private_key" node in the JSON configuration file.

When a new service account is created, you can download a JSON file with all configurations. This file can be processed by the FCM component, just call the method LoadSettingsFromFile and pass the JSON filename as argument. 

Sample

Find below a simple example to send notifications using FCM and JWT as authentication method.

oFCM := TsgcHTTPGoogleCloud_FCM_Client.Create(nil);
oFCM.GoogleCloudOptions.Authorization := gcaJWT;
oFCM.LoadSettingsFromFile('sgcfirebase-7x92e-5c80b8506a6c.json');
oFCM.GoogleCloudOptions.JWT.Subject := GoogleFCM.GoogleCloudOptions.JWT.ClientEmail;
ShowMessage(
  oFCM.SendMessage('Project-id', 
  '{"message": {"topic": "news","notification": ' +
  '{"title": "Breaking News",' + 
  '"body": "New news story available."},"data": {"story_id": "story_12345"}}}')
); 

Compiled Demo