Cannot link Unity to Visual Studio 2013 Community


I am trying to connect Visual Studio to Unity using VS Tools for Unity 2013 and I have completed all the steps listed in the documentation and tutorials: I have imported Tools package into Unity, generated projects files through Unity and opened the project up in the Visual Studio.

The problem is, the link icon in the bottom right corner of the VS IDE has the red x icon next to it which of course means: “not connected”.

After clicking said icon and choosing my active unity instance from the pop-up window, nothing has changed.

Please advise. Note: I have already tried everything with the Windows firewall, even disabling it.

Apply these step may be it works :
1.Check your Unity3d include VS tool or not
[you can check this by going help → about unity then in left bottom there should be a line like this visual studio tool enable some thing]
2.Check your visual studio is selected in Edit → preference → External Tools → Externel Script Editor
3.Last step is Chack your script open by right click and sync Script option or open c# project.

One last thing if you use Visual studio 2013 you should use visual studio tool for 2013 .

I’ve got the same problem, uninstall 2013 and install 2015 is good choice