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

Reproduce the Windows server/client scenario with the commands and network disconnect described in the issue, then inspect how the server handles the disconnected ESTABLISHED connection and how `iperf3 -h` exposes timeout options. Done means the server no longer leaves the connection stuck and the reported command-line parameters are resolved consistently.

Written by the indexing model from the issue text.