Troubleshooting Network Connections

I have a few apps that won’t connect on this machine, but do connect on older OSX machines over the same internet connection.

Where do I start troubleshooting the connections?

I’ve tested Fedora and Debian VMs with the same apps.

I’ve tested the apps on older OSX devices… they connect.

I’ve tested thru tor vs not.

I’ve tested thru ETH vs Wifi…

No luck getting these apps to connect.

Somewhere/somehow the connection is getting blocked.

I suspect firewall issues… but unsure how to troubleshoot that?

I’ve tried making some disposable qubes that connect directly to sys-net to rule out firewall issues. Still have the same problems.

The apps are torrent clients, VPN clients, and some crypto wallets.

What would be the usual suspects causing these symptoms?

You need ‘tcpdump’ on each box/VM. This tool will show you the network traffic, so the basic steps are:

  1. tcpdump on the VM/box where the app runs.
    then you will see if doing any traffic or not.
    if not then the issue is within the app.
    if yes, go to the next hop

  2. tcpdump on the next box/VM (sys-firewall, sys-net - depends on your virtual network topology.)
    tcpdump here to see if your traffic pass by…
    if not, then something blocking on this machine
    if yes, go to the next hop

  3. repeat until you found where your traffic stops.

If oyu have a woring one, that a good start to see how it is goes if working… then you can compare.

Sure, this assume some basic networking knowledge, and to know how to use tcpdump.


I think it might have something to do with UDP connections getting blocked.
Would they be blocked at the firewall level or somewhere else?

That is why I asked you about sys-whonix. No udp via tor.