Re: Recent issues with ports already in use

iain macdonnell - N6ML

On Mon, Feb 8, 2021 at 10:54 AM Dave AA6YQ <> wrote:

+ AA6YQ comments below

Ever since a recent Windows update, I'm dealing with much more frequent instances of DXLabs complaining about ports already in use...pretty much from every application. The weird thing is, I've run TCPView <> multiple times, and it never shows any port in DXLabs' range as being in use for either the "Local" port or the "Remote" port.
That is a bit weird. Did you sort by the "Local Port" column? Also
make sure that Options -> Show Unconnected Endpoints is enabled.

+ The "port in use" message comes from Windows, so either Windows or TCPView is not working correctly. Maybe TCPView isn't showing ports in use for UDP or Telnet or ....
Would another process binding a port for UDP prevent its use for TCP?
Theoretically, I think, it shouldn't, but I don't know Windows well

In any case, TCPView should show UDP bindings.

I've read some other posts about the possibility of Windows using ports in this range as ephemeral ports, and my experience may bear this out. I can often reboot, and then DXLabs can get the ports.

I'm wondering if anyone else has run into this recently or perhaps played with different Base Port settings?
The default dynamic port range for Windows 10 starts at 49152 and goes
up 16384 from there. You can check it (and change it, if you're
feeling adventurous) with "netsh int ipv4 show dynamicport tcp".

Looking at my desktop with TCPView, I see a lot of outbound
connections with source ports in the 52xxx range and up. It hasn't
been a problem for me, but I usually start the DXLab Suite apps (the
ones that I use) immediately on boot, and keep them running all of the
time. If you run them more sporadically, there's probably a higher
probability of some other process grabbing the port. Something below
49152 would probably have a better chance of being left alone.

If rebooting fixes it (temporarily), it does sound like you're
competing for those "dynamic ports".


~iain / N6ML

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