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Unavailable ports?

hotfingers
Newbie
Posts: 8
Registered: 24-01-2015

Unavailable ports?

I'm trying to open ports 5900 - 5902. I can open and close 5900 happily. If I close 5900 and try this for 5901 or 5902 using the same computer, same fixed ip address, firewall off, then they do not open.
I had this result with the old Technicor TG582n and well as with a new TP-link w9980.
To be clear, the only change in my test setup is the port number - evrything else remains the same.
I'm therefore wondering whether these ports above 5900 are reserved in some way and cannot be opened. They don't appear in any official list that I can see.
Any thoughts very welcome!
7 REPLIES
Plusnet Help Team
Plusnet Help Team
Posts: 12,859
Thanks: 115
Fixes: 35
Registered: 27-04-2007

Re: Unavailable ports?

Hi hotfingers,
From what I've been able to find out those ports are reserved for VNC, I'm not aware of any reason why you'd not be able to open those ports specifically though.
If you want it might help to let us know what the broader reason is that you're trying to do this in case we're able to offer an alternate solution for you.
If this post resolved your issue please click the 'This fixed my problem' button
 Adam Walker
 Plusnet Help Team
Community Veteran
Posts: 1,829
Thanks: 93
Fixes: 5
Registered: 21-01-2013

Re: Unavailable ports?

Would it not have been better to keep this in your previous thread?
Could the problem be with the way you're testing for open ports rather than the port not being open?
With a web site based test the port will only show as open if there's a server running the target port on the target device.
hotfingers
Newbie
Posts: 8
Registered: 24-01-2015

Re: Unavailable ports?

npr - this post was more specific in asking whether there was anyway that these ports might be reserved and unavailable via PlusNet.
I am aware of the need to have a server running through the target port. I tested 5901 and 5902 on exactly the same setup as 5900, which works. Addressing the same machine with the same fixed ip address and with the firewall off.
I fully accept that there maybe an issue here about which I'm unaware but I'm pretty sure I have the basics right. The only variable is the port number.
I can use the router's webpage to turn on 5900 and to turn it off - as shown by checkmyports.net. This has no effect for the other ports.
Adam - the reason for this is that I want to have remote access to three separate machines. I would therefore have each machine with a fixed ip addressed by its own port. It seemed logical to use ports in the usual vnc range - maybe not?
hotfingers
Newbie
Posts: 8
Registered: 24-01-2015

Re: Unavailable ports?

Following another post I now have a solution. Not one I had expected but having mapped the other ports to 5900 on each machine there now open. Thanks for taking the time to read and reply.
Community Veteran
Posts: 1,829
Thanks: 93
Fixes: 5
Registered: 21-01-2013

Re: Unavailable ports?

I see you've now found a solution but as I had already done the test I may as well post the result.
I tried opening those ports (TCP and UDP) here on my plusnet connection. -- no problems whatsoever.


hotfingers
Newbie
Posts: 8
Registered: 24-01-2015

Re: Unavailable ports?

That's very kind. Yes - I've done a workaround but I still don't understand why I can't actually open those ports directly. At least we know it's possible.
Thanks again.
Community Veteran
Posts: 4,980
Thanks: 376
Fixes: 16
Registered: 10-06-2010

Re: Unavailable ports?

Quote from: hotfingers
I am aware of the need to have a server running through the target port.

So, what happens if you try to connect to port 5901 or 5902 on the local computers? It sounds like you can open ports 5901 and 5902 on your external IP, but there's nothing receiving on those ports on the target computers.