Is it possible to use the Rest API or write something with sockets to connect the database and the mobile application?

Question

API

There is a test mobile application (student project), the user has the ability to authorize, as well as receive files such as pictures or videos from the hosting / server, which is better to use from the above, or both, (mobile application in java, what I ask in c#)
PS: regarding the languages, I will repeat this way, because it is a student project, we will not change them

Answer 1

what i ask in c#

it's vague. backend in C# or what?
you can both Rest API and sockets - what do you want? what can you do? then make
a backend in C# - this is now most convenient on .Net Core WebApi , in fact it is REST. authorization and the main logic of what to do
sockets are needed for stable and high-speed things like real-time chats. but in the same place in .Net Core there is a SignalR technology for this. we look at the docks, examples, connect and forward
pictures can also be given via WebApi, especially if they are not very large. but if there are a lot of them, it's static, and if there is free access, you can give a link through WebApi and just upload
a video - roam from the word streaming
if .Net Core is not suitable for some reason. for example, already started on the classic, all these technologies came from the classics . they're just better off the bat. the old classic is no longer being developed. by the fall or by the end of the year there will be DotNet 5 . the next generation of dotnet, which will replace both the crust and the classics. again there will be one dotnet, but already cross-platform completely

Answer 2

I'll expand on my previous answer.
If the backend is in Java. Use one of the modern microframeworks: Quarkus or Micronaut.
I recommend Quarkus. Entry threshold is lower. Finish the project in an hour or two. I recommend this tutorial . The database is configured via config, standard Java pojos for entities.
As a result, get a microservice for a native application. You can use it immediately in any docker project.
PS There is my Cart in the profile. There will be questions - write. I will answer.