Solved Your connection timed out ??? How to fix?

What @Quinneczech said, otherwise it's a guessing game. Following could be a reason: crappy internet connection, temporary internet issues, faulty network card, OS issues, corrupted game files, other PC issues. My suggestion is to start with a complete game reinstall and if that doesn't work perform an OS reinstall.

PS: @prisoneer, you do realize @Quinneczech's initial answer answer is based on your question that lacks any helpful details right? Don't be rude and expect others to read your mind, offer as much information as possible not just telling us the error and expect some magic instant fix because most of times it doesn't work that way. Any information at all such as pc specs, operating system, game version, where is your game installed, running the game in full screen or window mode, through which executable you run the game from, etc give us a starting point.

 

When i have 2 chars from same account logged on in the same game and leave game with 1 char.
Or 1 char in chat and 1 in-game from same account.

 

You would be amazed how many people still use XP. https://mygaming.co.za/news/pc/116211-this-is-how-many-people-are-still-using-windows-xp.html
About ~10% still use XP so that's a lot and when it comes to diablo2 it's quite a common used OS especially for those who don't hold a legal W7,W8,W10 license.
Compatibility mode in newer OS is not required unless you have problems in starting the game.

First of all I've mentioned few of the possible causes that could lead to that but troubleshooting isn't always easy.
Having internet problems doesn't guarantee that all game clients shall be affected, for example if you're loosing a lot of packets on the way some of the idling clients will not use as much bandwidth as other more active already open clients. Once again, that's only an assumption there could be a lot of other different reasons but may as well be network related.

If this was patch related, then everyone would have your issues. This alert message you're getting is client sided, meaning it comes from your end.

More clients = more internet bandwidth usage, more packets are being sent, etc. As far as I can see on google people advice on deleting `bnetcache.dat` files, reinstalling the game and/or the operating system and checking your connection which is being mentioned a lot.

 

@prisoneer, that's irrelevant as they are different games and they make use of resources in a different way, besides you're the only one getting this. Isolated scenarios similar to your problem can be found on d2jsp and so far the connection has been brought up most times into the discussion. For example one of the threads I've read says the guy experienced the same thing as you did while being connected to it's router but everything was fine while being connected to the modem. Do you have a laptop or something to test it out on a different pc?

As @Quinneczech said, make sure you're not logging in with two characters stored on the same account otherwise you will be kicked back at the login screen everytime when you leave a game. Additionally make sure you are not running illegal 3rd party softwares and complete a scan of your computer to make sure you're virus free.

 

You can make some easy tests if want.
1. take your laptop to visit some friend or familly member with DIFFERENT type of internet connection ideally and play there if it is the same, so probably it is in your laptop.
2. Bring to your home other PC (still friends or familly can help i think) install D2 and play...
3. If you use any switch or routers, remove it. Connect with cable to first place where you can connect. Example : I have ADSL connection, so i remove bouth of my router on the way and I connect to modem (first place where i can plug in my cable)
SURE DONT USE WIFI FOR TESTS !!!!