SERT 2.0 should run under the conditions that you describe without any modifications to any of the SERT files. You should run clean.bat before starting serthost.bat first on the server, then launch the SERT GUI. Again, please make sure you run clean.bat before beginning.
The issue that you report is often due to firewall issues. Please make sure that the firewall is completely turned off and verify that the problem reproduces.
If the problem reproduces, please make sure that the 64-bit version of Java is installed:
C:\Users\Van>java -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)