How to implement user specific requests between client and server?

Question

Information Security

There is a server and a client where the user is authorized. How can you implement the execution of client requests for a specific user?
As the simplest - remember when authorizing ip and each time check from which ip the request comes, but this is not safe (man-in-the-middle)
Send the encrypted user password each time and check with each request? Encrypt Request IDs?
How to do it correctly, optimally and safely?