German Kommunikation between Android and PC

Hello,

I need a simple example of Network Tutorial with bidirectional communication.

I send strings of smartphone to the PC and it works.
But if I send strings from the PC, then I don't know how to take the data.

In VB6, there is the sub Winsock_DataArrival (byte).
In B4A I miss that.

I hope you can help me. thnks!
Sinan