Enabling Offer-based Remote Assistance
Add the following entry to the Windows Firewall: Define port exceptions setting:

• 135:TCP:*:Enabled:Offer Remote Assistance
 

Add the following entries to the Windows Firewall: Define program exceptions setting:

• %WINDIR%\PCHealth\HelpCtr\Binaries\Helpsvc.exe:*:Enabled:Offer Remote Assistance
 
• %WINDIR%\PCHealth\HelpCtr\Binaries\Helpctr.exe:*:Enabled:Remote Assistance – Windows Messenger and Voice
 
• %WINDIR%\SYSTEM32\Sessmgr.exe:*:Enabled:Remote Assistance

Note For computers running Windows Server 2003 with SP1, do not add the exception for Sessmgr.exe. Instead, enable the Windows Firewall: Allow Remote Desktop Exception setting.

Note  By opening TCP port 135, you are also allowing Remote Procedure Call (RPC) traffic.