It's rather irritating that messenger disconnects from the internet when I close my laptop/put it in standby until I log in again and continue use. I'd like to prevent this as I usually have several conversations open and dislike the fact that I have to sign into the messenger again in order to continue speaking and by then some of the people I was talking to have already left. So, in other words, how can I keep messenger from signing out when I enter the user screen/have the laptop in standby? I googled this, yes, but had no results.

In power saving modes your computer isn't on so the Internet shuts off which disconnects you. Don't go saving power when you don't want to shut down critical components.
There's no way around it except using a mobile phone or something similar to keep the connection.