Hi Vasilis,
How frequent are you getting this log? As in the above log, I can see it has come only once which normal case. This can occur due any kind of interrupt which can impact socket connectivity between device and server. Some of the reasons can be an intermittent network, call, any activity on a device which can put it in the background etc.
I have performed testing on my iOS Sample and below are the logs:
AppWarpTrace: -[WarpClient raiseConnectionListenerWithResult:]..result=0
2017-12-12 17:39:31.267726+0530 AppWarpSDKSample[8856:2878218] onConnectDone = 0
2017-12-12 17:39:31.268465+0530 AppWarpSDKSample[8856:2878218] Connected Successfully
AppWarpTrace: sending assoc udp
AppWarpTrace: isAssocPortSent = 1
AppWarpTrace: -[ClientChannel onUdpSocket:didReceiveData:withTag:fromHost:port:]
2017-12-12 17:39:31.488869+0530 AppWarpSDKSample[8856:2878218] -[WarpClient handleAssocUdpPortResponse:]....SUCCESS
AppWarpTrace: -[WarpClient fireUDPEvent:]
2017-12-12 17:39:31.489108+0530 AppWarpSDKSample[8856:2878218] UDP connected succesfully
AppWarpTrace: isAssocPortSent = 1
2017-12-12 17:40:08.840020+0530 AppWarpSDKSample[8856:2878218] -[ZoneListener onGetAllRoomsDone:]
2017-12-12 17:41:16.549833+0530 AppWarpSDKSample[8856:2878218] -[ZoneListener onGetAllRoomsDone:]
2017-12-12 17:42:45.206742+0530 AppWarpSDKSample[8856:2878218] Joined successfully
2017-12-12 17:42:45.207067+0530 AppWarpSDKSample[8856:2878218] Name = mainLobby
2017-12-12 17:42:45.207233+0530 AppWarpSDKSample[8856:2878218] Owner = admin
2017-12-12 17:42:52.922570+0530 AppWarpSDKSample[8856:2878218] -[ZoneListener onGetMatchedRoomsDone:]
2017-12-12 17:45:16.884397+0530 AppWarpSDKSample[8856:2878218] -[ZoneListener onGetAllRoomsDone:]
AppWarpTrace: NSStreamEventEndEncountered : 5
AppWarpTrace: Error 0: (null)
AppWarpTrace: -[WarpClient onConnect:]..value=0...connectionState=3..sessionId=-2054021032
AppWarpTrace: DISCONNECTING.....
AppWarpTrace: -[WarpClient fireDisconnectEvent:]
2017-12-12 17:45:32.997311+0530 AppWarpSDKSample[8856:2878218] Disconnected succesfully
In the above log, you can see that I was connected to the server around 6 mins then I called disconnect API.
Please let me know if this is not the case.
Thanks.