Hi, I have a similar problem and I don't know if I'm doing something wrong or if it's a bug. I have a client on iOS that sends a UDP message to a server programmed in Java. Once the server receives the message it responds with a UDP message. The client gets the message and all is well. But when I run the following scenario, I get an error message: 1. I start the client and an instance of NWConnection is created. 2. the connection is started with connection.start(...) 3. directly after the start I execute the command: connection.receiveMessage(...) 4. the server is NOT started 5. the created NWConnection is in "Ready" state 6. i send a message 7. the passed "NWConnection.SendCompletion" is called without error. Otherwise nothing happens here. No errors. 8. i start the server 9. i send a message again 10. the message arrives at the server. Then the server sends a UDP response. 11. On the client I now get the following message in the console = "2021-04-10 12:30:43.660695+0200 MySocketClient[27462:5157187] [connection] nw_read_request_report [C1] Receive failed with error "Connection refused"" 12. my response handler is called "(data: Data?, context: NWConnection.ContentContext?, isComplete: Bool, error: NWError? )". Interestingly, I get an error = POSIXErrorCode: Connection refused. But at the same time data contains the correct content sent by the server. 13. If I now send further messages from the client to the server everything runs as described from step 6 to step 12. Am I doing something wrong here? If not, maybe my description can help.