startWebLogic: maximum number of socket reader threads allowed by the configuration is: 4

I am running Weblogic 12c 12.1.1 which I installed from the zip archive downloaded from the Oracle webpage on windows 7 64bit, using a Java 7 64 bit JVM.

When starting WebLogic I had this error message: <BEA-000402> <There are: 5 active sockets, but the maximum number of socket reader threads allowed by the configuration is: 4. You may want to alter your configuration>

My settings in the WebLogic Administrator Console indicated that I was using native I/O, so the configuration seemed fine.

However, earlier in the logs I also had this warning:
<BEA-000438> <Unable to load performance pack. Using Java I/O instead. Please ensure that wlntio.dll is in: C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;...

I found wlntio.dll in %WL_HOME%\server\native\... subdirectories for different platforms. Apparently this had not been added to the startup configuration, because I did not run an installer, but installed from the zip file. I added the directory in wich the dll lives to the PATH in the startupscript  ...\weblogic\domain1\bin\setDomainEnv.cmd:

set WL_HOME=C:\java\weblogic\12.1.1\wlserver
@REM added the next line
set PATH=%WL_HOME%\server\native\win\x64;%PATH%

Now all's well :)