I'm on Steam, and the game has connection errors on startup

If reinstalling doesn't help try these connection troubleshooting steps. 

There are a number of issues that might cause connection problems on Steam. If reinstalling doesn't help you, try these detailed troubleshooting steps. These are listed from most common to least common:

1. Disable IP Helper

• Press the keys "Windows" and "R" simultaneously. (Windows normally between Left Alt and Left Ctrl)
• Type "services.msc" in the field and hit enter.
• Scroll down and find "IP Helper" in the list.
• Right-Click on "IP Helper" and select "Properties."
• Change "Startup type" to "Disabled."
• Stop the service
• Click "Ok."
• Reboot your machine.

2. Disable Windows Firewall and Windows Defender

If you're uncomfortable disabling your PC security, please skip this step (see 3 below for some other options)

• Press the keys "Windows" and "R" simultaneously. (Windows normally between Left Alt and Left Ctrl)
• Type "services.msc" in the field and hit enter.
• Scroll down and find "Windows Firewall" in the list.
• Right-Click on "Windows Firewall" and select "Properties."
• Change "Startup type" to "Disabled."
• Click "Ok."
• Follow these same steps for the "Windows Defender" Service.
• Reboot your machine.

3. Configure your firewall(s) and Anti-Virus(es)

Even when properly configured, the disabled modes or exceptions lists often do not function properly for 3rd party firewalls. It would be much quicker to temporarily uninstall your firewalls from your computer. This would allow you to quickly rule them out as a potential cause of a problem.

If you're uncomfortable uninstalling your anti-virus and firewalls, a good alternative is Avast, which is free for home use. It even has a disabled/gaming mode: Click Here


4. Disable your IPv6:

• Windows 7: Click Here
• Windows XP: Click Here

5. Syncing your windows Clock

• Click the clock in the bottom right.
• Click "Change Date and Time settings"
• Click the "Internet Time" tab
• Click "Change Settings"
• Select your time server amd click "Update Now"

6. Change your DNS

• Try using Google Public DNS: Click here for a walkthrough
• OpenDNS may help in this case. Click Here for a walkthrough

This excellent list of fixes was based on findings of someone named Eliot from the League of Legends Forums (League of Legends PvP.net also uses Adobe Air). You'll probably never read this Eliot, but thanks for the list of things!