iOS background mode, in which applications and how is it arranged?

Question

iOS

Good day to all!
Recently I encountered the fact that I can not find normal applications with work in the background:
1. IRC clients - all the clients I found in the Appstore have a connection in the background, which nullifies the whole point of these applications.
2. SSH clients and all sorts of applications for monitoring servers - in the background, the SSH connection falls off, monitoring programs work only if they are not minimized, in general, some kind of nonsense.
The information that I found in Google cannot be understood without a normal explanation, the only thing I understood is that not all applications can fully work in the background, but only a number of allowed ones, such as:

1. audio players
   
2. all sorts of voip
   
3. navigation apps
   
4. all sorts of voip
   
5. all sorts of stalls
   
6. all sorts of accessory applications
   

But don't applications for SSH, IRC fall into any category?
Are there active IRC and SSH users on iOS?

Answer 1

Nothing works in the background without a jailbreak. This is Apple's official policy. And if you need it in the background - google jail.
And what is allowed works in a special way:
-voip applications are allowed to hold a tcp socket + perform a quick ping operation once every n minutes. + remote push notification -
for everything else there is a master card.... it is possible to schedule some kind of long-term operation in the background, which will twitch the OS at its discretion. Used to fetch data from the server