CS:GO - Playing with friends - LAN Settings
If you and your friends are playing from the same house in a LAN setting you will need to ensure everyone is using a different public port to be able to connect to our servers.
How can you do this?
This a quick and simple thing you can do with plenty of time to be able to join and play the match.
Go Into Your Steam Library and right click on CS:GO/Dota2 scroll down to properties.
A new window will pop up choose “Set Launch Options…” in the launch options window, write "+clientport 2700X" X = 6/7/8/9(Default = 27005)
Then choose “OK” and close the other window as well and start up your game and join the match by pressing play or joining with the IP provided in the match room for CS:GO or accept the invite from the bot in your Dota2 game.