Taken from https://social.msdn.microsoft.com/Forums/en-US/df043823-ffcf-46a4-9e47-1c4b8854ca13/troubleshooting-guide-for-visual-studio-test-controller-and-agent?forum=vststest

1) Close VS
2) Create my.pkgdef file under C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\Extensions\my\ with the following content:
[$RootKey$\EnterpriseTools\QualityTools\ListenPortRange]
"PortRangeStart"=dword:00000400
"PortRangeEnd"=dword:00000401
3) Start VS
4) Start regedit.exe and check if new values are now under (32 bit registry) HKCU\...\10.0_Config\EnterpriseTools\QualityTools\ListenPortRange. If they are not there, close VS, remove the 10.0_Config node and start VS again.
Note that the name of the file and directory does not really matter, what is important that:
A) The file has extension .pkgdef
B) It's under C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\Extensions directory (could be in a subdirectory of it).