Steam Network Issues

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I’m constantly getting disconnected from the Steam Network. If I look at my friends list, it says I’m offline. This appears in a chat window if I have it open.
Your state is set to Offline.
[Friend] is now Offline.
Lost connection to Steam, will rejoin chat automatically when connection regained.
Connected again and rejoined chat.

This happens in sync with me getting disconnected from a Garry’s Mod server I’m on for either “Client Timed Out” or “Could not connect to VAC servers.”
I also get disconnected from other games like CS:S or TF2.

DO NOT SUGGEST:

That is is a network issue. It isn’t. My ports are open, everything is set up. Also, my friend can come over with his laptop, connect WIRELESSLY, and have NO issue.

That this is because of F2P TF2. That happened days ago, and I’ve been getting this problem for a year or two now.

The only thing I can guess that’s causing this is a bad network card or conflicting programs, but I’ve uninstalled nearly everything that is listed on Steam about conflicting programs.