iperf3.21 server end stuck in ESTABLISHED state when disconnected network

1,setup server end in windows: iperf3.exe -s -p 5201 -i 1 --rcv-timeout 60000 --idle-timeout 30 2,setup client to connect the server running traffic 3,disconnect the client's network 4,check the server end after few minutes use "netstat -ano | findstr 5201" checking and still found an ESTABLISHED link it means iperf server get stuck. 5,also not found "--cntl-ka" "--snd-timeout" parameters in iperf -h