Client (android)-server (ubuntu server) application. How to organize?

Question

PHP

I have an idea for a startup. General essence: there is a site with a mysql database, a service is registered on it, customers register and look for the service they need, negotiate with the service provider. The site is self-written (php, js). What you need: this whole idea needs to be implemented additionally in the form of a client-server in order to increase the efficiency of client notifications. The client role is an android application, and the server role is ubuntu server. Question: How can this be better organized? How to write an android-friendly application-server Under ubuntu? As I see the work of this bundle: on the andriod client, a login and password are entered and all this is sent to the server with the login command that you need to log in and wait for a response from the server. The server application on ubuntu sees the login label, and compares the login and password hash in the mysql database. If everything is OK - hangs the client on a unique port (and how else to distinguish the client from each other?) Sends the is_data command and a data packet to the client. The client receives all information on the smartphone screen. And another question: how to properly organize communication between the server and the client to get new information in the database instantly by the client? Should the client poll the server periodically? What if there are many? Or all the same, the server sees that new information is sent to all logged-in clients. Is python suitable for creating a server application? how to properly organize communication between the server and the client to get new information in the database instantly by the client? Should the client poll the server periodically? What if there are many? Or all the same, the server sees that new information is sent to all logged-in clients. Is python suitable for creating a server application? how to properly organize communication between the server and the client to get new information in the database instantly by the client? Should the client poll the server periodically? What if there are many? Or all the same, the server sees that new information is sent to all logged-in clients. Is python suitable for creating a server application?