Aftrer updating to 2.9.12 the issue is gone. Thank you.

13.07.2021 18:40:41:DEBUG: 1: Connecting to InterNetwork/smpp.smsc.ru:3700
13.07.2021 18:40:41:INFO : 12: 192.168.100.3:60094 => InterNetwork/smpp.smsc.ru:3700 Connection established.
13.07.2021 18:40:41:DEBUG: 5: Send PDU: BindTransceiver, Sequence: 1
13.07.2021 18:40:41:DEBUG: 5: PDU Received ...

We use 2.9.9 version. How can I switch on and use logging functionality?
We don't subscribe on evDisconnected.
We use only connectasync, bindasync and sendasync and evDeliverSm handler.

SmppClient.DisconnectAsync lasts about 60 seconds. SmppClient.Disconnect lasts the same time as well. We works with Smsc.ru. ConnectAsync and BindAsync work succesfully and last about 1 second.