nw_socket_get_input_frames [C4:1] recvmsg(fd 35, 9216 bytes) [61: Connection refused]

We're using the Network.framework and send data between an iOS app and a macOS app. Works great. Until it doesn't.

When I stop using the iOS app for like 2-3 minutes the connections stops working.

The debug log of the macOS app says: 2020-12-01 22:40:40.274638+0100 Remote for Zoom[10750:497151] [] nwsocketgetinputframes [C4:1] recvmsg(fd 35, 9216 bytes) [61: Connection refused]

Can someone translate this into English? Tried the google traslator but...

On a more serious note, what is this and how to heal it? Does the 2-3 min pause as symptom / trigger of the above error message ring some bells?