Firewall problems with NoMachine

Could not find a general “Networking” section so I am going to try here.

Ok, I am having problems with my firewall setup. I have NoMachine installed on all of my computers: A server with Debian, a desktop with Endeavour, a laptop freshly installed with Endeavour, and another laptop with Garuda. Both the server and desktop connect to each other just fine and both laptops connect to the server and desktop, but there is no access into either the Endeavour or Garuda laptops. I can see them after setting up the firewall (TCP 4000 and UDP 4011-4999) but I get the error:

“The remote host ‘192.168.1.x’ refused to establish a network connection on port ‘4000’. Please verify that NoMachine is correctly installed and listening on the port where you are trying to connect, and that incoming traffic is not being blocked by a firewall or NAT.”

The desktop has an older install of Endeavour and so did the laptop, but I did a new install with the current ISO and now it does not work. I don’t know enough about firewalld to troubleshoot it.

Thanks.

Hi,
https://kb.nomachine.com/AR10R01099
Have a look at it.

That link looks to be related to port forwarding. All these computers are on the same network and when I do connect to them remotely I use Tailscale so port forwarding and NAT do not apply in this case.

Also, the issues above are replicated when routing though Tailscale.

Any ideas? It is like there is another firewall blocking it.

Here is what I get on the Desktop:

 jeremiah  LR-Desktop  ~  sudo firewall-cmd --list-all
[sudo] password for jeremiah: 
home (active)
  target: default
  icmp-block-inversion: no
  interfaces: eno1
  sources: 
  services: dhcp dhcpv6-client dns ftp kdeconnect mdns samba samba-client samba-dc ssh transmission-client vnc-server wireguard
  ports: 8622/tcp 4000/tcp 4011-4999/udp
  protocols: icmp ipv6-icmp
  forward: yes
  masquerade: no
  forward-ports: 
  source-ports: 
  icmp-blocks: 
  rich rules: 

 jeremiah  LR-Desktop  ~  nmap -p 4000 localhost
Starting Nmap 7.93 ( https://nmap.org ) at 2022-12-29 23:38 CST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000096s latency).
Other addresses for localhost (not scanned): ::1

PORT     STATE SERVICE
4000/tcp open  remoteanything

Nmap done: 1 IP address (1 host up) scanned in 0.98 seconds

Here is the laptop:

 jeremiah  JLaptop-Endeavour  ~  sudo firewall-cmd --list-all
[sudo] password for jeremiah: 
trusted (active)
  target: ACCEPT
  icmp-block-inversion: no
  interfaces: wlan0
  sources: 
  services: kdeconnect samba samba-client wireguard ws-discovery
  ports: 8622/tcp 4000/tcp 4011-4999/udp
  protocols: 
  forward: yes
  masquerade: no
  forward-ports: 
  source-ports: 
  icmp-blocks: 
  rich rules: 

 jeremiah  JLaptop-Endeavour  ~  nmap -p 4000 localhost
Starting Nmap 7.93 ( https://nmap.org ) at 2022-12-29 23:40 CST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00024s latency).
Other addresses for localhost (not scanned): ::1

PORT     STATE  SERVICE
4000/tcp closed remoteanything

Nmap done: 1 IP address (1 host up) scanned in 0.09 seconds

I am stuck at this point. I really need to redo my desktop since I have a faulty drive but I cannot do this until I can fix this issue since I use NoMachine almost daily on the desktop.