WiFi Communication between PC and Android Problem

Hi all,

I am trying to establish bidirectional communication via Wifi between an Android device and a PC running Windows. I have followed the Daniel Sauter's book "Rapid Android Development", Chapter 6: Networking devices with Wifi. https://www.mobileprocessing.org/networking.html
I am trying the first example of the chapter.

On the Android side, the code can be found at:

https://github.com/danielsauter/rapid-android-development/blob/master/code/Networking/WiFiDataExchangeAndroid/WiFiDataExchangeAndroid.pde

On the PC side, the code can be found at:

https://github.com/danielsauter/rapid-android-development/blob/master/code/Networking/WiFiDataExchangePC/WiFiDataExchangePC.pde

When running both codes, the android device gets the messages from the PC but the PC doesn't get the messages sent by the Android device. Is there any solution? If not, Is there another approach to establish the communication using Processing?

I am using:

PC: Windows 10 v.1709, Processing 3.3.6, Android Mode 4.0, Ketai 14, oscP5 0.9.9

Android device: Samsung S5 Mini (SM-G800F), Android 6.0.1

Thanks in advance!