iPhone prevents High Sierra from sleeping (constant connections attempts with TCP)

Hello,

my iPhone 6s plus (iOS 11) permanently prevents my mac (High Sierra) from sleeping. As wake reason the terminal tells the following:

localhost kernel[0]: (AppleBCM5701Ethernet) AppleBCM5701Ethernet [en0]: Wake reason: Enet.Service - Connection attempt with TCP from xx:xx:xx:xx:xx:xx 192.168.188.44.62425 to 192.168.188.37.49177

These messages appear every 5 to 10 minutes in the syslog (called via "log show --style syslog --start "yyyy-mm-dd" | fgrep "Wake reason"").

192.168.188.44 is my iPhone, 192.168.188.37 is my Mac mini running High Sierra. Port 49177 is assigned to the process "rapportd" on the Mac.

I deleted all apps on the iPhone which have a potential to access my Mac mini. I also logged off from iCloud on the iPhone, turned off synchronization of iMessage etc. But no luck. Something still wakes the Mac mini.

I ran Yosemite before switching to High Sierra recently. I always had sleeping issues with the Mac mini also with Yosemite. So I assume that the issue has nothing to do with High Sierra in particular.

I appreciate any ideas how to solve this.

Regards

Hartwig