How does the Server side of the mobile application work?

Question

Mobile development

hello! I googled a lot on this topic, the problem is not that there is no information, but on the contrary, there is so much of it that there is porridge in my head, I asked questions on the forums, but there was no way to answer my question, I hope everything will finally clear up here.
I wrote an application in JAVA for android, the essence of the application is in viewing content that was in the application itself, that is, the server was not needed at all, but there were changes in applications, now you need to connect to the server to receive data in the form of pictures and text, as well as now I would like to add user registration, the ability to send user messages to another user. But for all these application functions, a server is needed and everything that is attached to support those application functions that I described
several questions and actually here they are:
the server has an operating system, there is the server itself with its characteristics, well, there is some kind of operating system, RAM, size of hard drives, etc.
1. What else is needed to support the operation of the application described above with the server? some kind of program written in some particular language to work with the client's application? should I write it myself? Or is it already in the form of templates?
2.How to transfer data (content requested by the client) from the server to the client? What is a specific protocol? Or is there any technology?
3.And if the number of users will be considered millions, how will the server work with them? while not falling?
I will be very grateful for your help ... I myself first encountered the server side of the application, and there are a lot of questions, but I would at least hear the answers to these ... it will already be great

Answer 1

It is very difficult to give an answer in a few words. My last article on Habré about a simple backend for a mobile application on Google App Engine + Go.
In terms of price/performance/scalability, GAE + Go is the best option, but without experience in this matter, it will be very difficult to write the required solution.
Another option - sites like parse.com - provide many features and services at, say, reasonable prices. They are distinguished by simple integration, on their website and on the network you will find a bunch of examples from which you can learn.
2. Everything over HTTP or HTTPS, the transmitted data is often serialized to JSON. The client makes requests to the server - this is the easiest option.
3. GAE will definitely do it. Parse, I think, too. It all depends on how efficiently resources are used and how much money is poured into maintaining the service. If you do everything on your own single server, then most likely it will not cope with the load, especially if some cheap VPS.
Finally, take a look at parse.com to get started.

Answer 2

you raise any web server and use a protocol such as HTTP for client and server interaction. What to write the server part on is a purely individual question, and there are enough options. For example php, ruby ​​and python and javascript

Answer 3

we have done on Ajax (in the webview + js application, on the php server), but probably it can be somehow cooler