Re: Connection port timeout

[Frediano Ziglio <freddy77@xxxxxxxxx>]

On Wed, May 14, 2025 at 11:23 PM 吴山 <shan.wu@xxxxxxxxx> wrote:

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@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@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@172-26-51-207 ~]# nc -zv 172.26.51.207 4100

Ncat: Version 7.70 ( https://nmap.org/ncat )

Ncat: Connected to 172.26.51.207:4100.

Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.

[root@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@172-26-51-207 ~]# nc -zv 172.26.51.207 4100

Ncat: Version 7.70 ( https://nmap.org/ncat )

Ncat: Connected to 172.26.51.207:4100.

Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.

[root@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@172-26-51-207 ~]# nc -zv 172.26.51.207 4100

Ncat: Version 7.70 ( https://nmap.org/ncat )

Ncat: Connection timed out.

It looks like you are testing from the same host but you already have a connection from a remote host.

This should not happen if you don't already have external connections.

 

此信件包含保密信息，请收件人予以保密，未经许可，请勿向第三人披露，谢谢。

This letter contains confidential information which is requested to be kept confidential by the recipient and shall not be disclosed to any third party without permission. Thank you.

Do you realize that if this is true you are violating corporate policies, right?

Frediano