[Play 2.7 Java] on Windows opens a random TCP Port

While debugging my application i noticed that play opens a random TCP port to localhost transmitting data. First i thought it came from a dependend library but finally i tried it with the simple Hello World application from lightbend, downloaded here (Play 2.7):

I guess the amount of messages increases with the amount of akka messages sent because in my application the amount of messages increases a lot by time.

Wireshark display as message content always the same value. Ascii 01.

My questions are: What is this connection necessary for? And is it possible to disable?