You can NOT send a push notification without using APNs. Why? first you need to understand how the technology works:
You need a certificate for a handshake.
You need a device token to be identified by APNs.
- In your app, you have to register to APNs.
- The app requests the certificate from APNs (handshake).
- The server sends back its certificate.
- The app will establish a connection to the server and send the PN certificate to the APN server.
- The server will validate that you are a trusted app.
- The app requests to create a token.
- The server creates a token and sends it back.
- In your app you save the token (to do e.g. push notifications to a specific user instead of a broadcast).
- End.
So, as you see, you need to establish a trusted connection, the APNs is responsible for creating a token to identify your device within the network, and will be responsible for sending notifications.
For more info you could see: Apple PNs