Connection port timeout

[吴山]

After executing the nc command twice, executing the nc command again timed out, and the netstat command showed that the server did not close the socket connection：
[root at 172-26-51-207 ~]# systemctl status usbredir-4100-003-002.service 
● usbredir-4100-003-002.service - /sbin/usbredirserver -p 4100 003-002
 Loaded: loaded (/run/systemd/transient/usbredir-4100-003-002.service; transi>
Transient: yes
 Active: active (running) since Tue 2025-05-13 14:13:41 CST; 12min ago
 Main PID: 3864277 (usbredirserver)
 Tasks: 2 (limit: 101063)
 Memory: 608.0K
 CGroup: /system.slice/usbredir-4100-003-002.service
 └─3864277 /sbin/usbredirserver -p 4100 003-002
5月 13 14:13:41 172-26-51-207 systemd[1]: Started /sbin/usbredirserver -p 4100 >
5月 13 14:13:45 172-26-51-207 usbredirserver[3864277]: usbredirparser: Peer ver>
[root at 172-26-51-207 ~]# rpm -qa | grep usb
qemu-kvm-hw-usbredir-6.2.0-232.g09252161d1.el8.x86_64
usbredir-0.12.0-2.el8.x86_64
libusbx-1.0.23-4.el8.x86_64
usbutils-010-3.el8.x86_64
usbredir-server-0.12.0-2.el8.x86_64
libgusb-0.3.0-1.el8.x86_64
[root at 172-26-51-207 ~]# nc -zv 172.26.51.207 4100
Ncat: Version 7.70 ( https://nmap.org/ncat <https://nmap.org/ncat > )
Ncat: Connected to 172.26.51.207:4100.
Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.
[root at 172-26-51-207 ~]# netstat -nap | grep 4100
tcp 0 0 172.26.51.207:47988 172.26.51.207:4100 FIN_WAIT2 - 
tcp6 1 0 :::4100 :::* LISTEN 3864277/usbredirser 
tcp6 1 0 172.26.51.207:4100 172.26.51.207:47988 CLOSE_WAIT - 
tcp6 0 0 172.26.51.207:4100 172.26.51.230:58576 ESTABLISHED 3864277/usbredirser 
[root at 172-26-51-207 ~]# nc -zv 172.26.51.207 4100
Ncat: Version 7.70 ( https://nmap.org/ncat <https://nmap.org/ncat > )
Ncat: Connected to 172.26.51.207:4100.
Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.
[root at 172-26-51-207 ~]# netstat -nap | grep 4100
tcp 0 0 172.26.51.207:47988 172.26.51.207:4100 FIN_WAIT2 - 
tcp 0 0 172.26.51.207:33384 172.26.51.207:4100 FIN_WAIT2 - 
tcp6 2 0 :::4100 :::* LISTEN 3864277/usbredirser 
tcp6 1 0 172.26.51.207:4100 172.26.51.207:33384 CLOSE_WAIT - 
tcp6 1 0 172.26.51.207:4100 172.26.51.207:47988 CLOSE_WAIT - 
tcp6 0 0 172.26.51.207:4100 172.26.51.230:58576 ESTABLISHED 3864277/usbredirser 
[root at 172-26-51-207 ~]# nc -zv 172.26.51.207 4100
Ncat: Version 7.70 ( https://nmap.org/ncat <https://nmap.org/ncat > )
Ncat: Connection timed out.
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