• If you are citizen of an European Union member nation, you may not use this service unless you are at least 16 years old.

  • You already know Dokkio is an AI-powered assistant to organize & manage your digital files & messages. Very soon, Dokkio will support Outlook as well as One Drive. Check it out today!


MLAT trouble-shooting

Page history last edited by info@coaa.pt 4 years, 1 month ago

There is a self-test URL here: http://www.coaa.co.uk/gs-mu-test.php, and self-help for Mlat setup is available in the main Plane Plotter Groups.io group: https://groups.io/g/planeplotter/


General Techniques


It may help in diagnosing problems when trying to perform Mlat requests, to recognise the various possible symptoms of failure and their probable causes.


When you Ctrl-left click on a 'position-less' aircraft in the View..Aircraft screen, several things might happen.


The aircraft on which you clicked, will become the designated aircraft and will turn red on the View..Aircraft screen.


In the title bar, you may immediately see a message like one of the following:


  • "No recent data for selected aircraft" - self explanatory.  Choose a different aircraft that is currently being tracked. 
  • "Insufficient raw data sharers" - self explanatory.  Choose a different aircraft that is being received by several active Ground Stations (GS).  Are you sharing?  If not, there will be no GSs in your list. 
  • "Sharing state incompatible with Mlat request" - self explanatory.  You are sharing in the upload-only mode and therefore cannot elicit the data from the sharing system.  Change the sharing mode (to two diagonal arrows) and try again.


If no such messages appear in the title bar, the program will try to initiate an Mlat request.


  • A pop up box will appear saying "Sending request".  In a second or so it should change to a countdown "Time remaining".  If the "Sending request" message persists for any length of time, then there is a problem accessing the Internet.  Check the permissions for Plane Plotter in your firewall.
  • At this point you might see a red alert box with the message "Multilat is not enabled".  In that case, you are not currently entitled to make an Mlat request.  You can either be validated as a Ground Station (providing raw data to other users) or you can request Master User status on a trial basis by visiting http://www.coaa.co.uk/mlat_request.php. 
  • If you see no red alert message and the pop up box simply shows the "Time remaining" message, the Mlat request has been accepted and you can be confident that you do indeed have Master User status. 
  • At the end of the minute during which incoming data is accumulated, you should see significant numbers in the various fields and, if there are sufficient hyper curves, the program will switch to the chart view and display the calculated position for your chosen target. 
  • If you get only a small number of responses, you may have chosen an aircraft that is not well covered, or your firewall may be blocking the incoming packets because it interprets the data stream as a Denial of Service (DoS) attack.  Try other aircraft but if the number is always too few, adjust your firewall DoS settings.
  • If you persistently get zero results at the end of the minute, then the incoming raw data is not reaching Plane Plotter at all.  Make sure you have opened the UDP port by selecting Options..I/O settings and enabling "UDP/IP data from net".
    Check your router port forwarding settings to make sure that the correct format (UDP), the correct port (9742) and the correct IP address (the machine running Plane Plotter) have been entered.


This is from a post on the Plane Plotter Yahoo group by Bev (Plane Plotter author):



Plane Plotter Settings


Make sure you have opened the UDP port by selecting Options..I/O settings and enabling "UDP/IP data from net".


Other Router Settings


When you get Mlat data from other PCs, these need to be forwarded to your PC as described above, and your router needs to be told which PC should get the Mlat packets.  However, in some configurations, or if your PC hasn't been used for a period, the router may assign a different IP address to your PC, and hence it won't get Mlat packets.  One thing you can do to reduce the chance of getting a new IP address for your PC - and hence losing Mlat capability - is to tell your router to allocate the addresses for a longer period.  Typically, addresses may be allocated for just 24 hours, so if you are switched off for the weekend you may get a new address on Monday!  To change this behaviour, go into your router and change the "lease time" to as large a value as is reasonable.  Unless you are running a service for the general public (with a daily turnover of connected devices), having a lease time of 30-45 days will likely meet your needs.  Even better is to set up a reserved address in your router for your PC, or to use static IP addresses as described below (under: Mlat stopped working).

On my DD-WRT router, this is in the Setup, Basic Setup tab, is called Client Lease Time, and is specified in minutes.  I have mine set to 60000 minutes (just over 41 days).

On my ISP-supplied Netgear WNR2000v2 router, you appear to be able to reserve IP addresses for PCs which need a fixed IP (like Mlat master users) - see Using Address Reservation in the manual.  You don't seem to be able to set the lease time for clients on the LAN.


Some PCs require a "Connection specific DNS suffix" for the LAN adapter, and some routers may require a "Host name".  You may not be able to connect properly if yours is blank.



Mlat stopped working


Q: I was running Mlat for a period of time OK, but when I rebooted after a day or two I can start requests but I get nothing back.

A: Check that the IP address of your computer and the forwarding address specified in your router still match.  You may want to reserve the IP address for your computer's MAC address in you router (see these notes), or move to using fixed computer IPs - a static IP address.  How do I get my PC's network card MAC address - see here. For some more information - see: http://portforward.com/networking/staticip.htm.  An alternative is to make the lease period much longer on your router (say 28 days(, see your router for details.


Q: If you plug the SBS to a different USB port after removing the SBS-1 connection, you may experience problems.
A: Always use the same USB port once you are set up.



Mlat from a second instance of Planeplotter on another PC


Q. I was recently accorded MU status on the second instance PP but although I can see positionless a/c in the list I have been unable to initiate Mlats. 

The mlat box appears and the countdown runs out, ending in 'insufficient data for fix', even on aircraft already showing in the chart.


A. Do you have two instances of PP on one router ?


Even if you have no receiver selected on the second instance which is on another PC and you can see mlats on a second machine if it is designated MU ,

you can't initiate manual mlats. 

The data for manual mlats can only go to the designated instance....your main GS / MU. 

If you try a manual mlat on the second instance the request will go out but the incoming packets will get lost.

The result is that on some occasions this can kill the MU on your main machine  too as the router gets confused.


So in summary , a manual mlat can only be requested from an instance which

is designated , by IP or ID in port forwarding.




Network test functions


From version 5.4.6 (upgrade here) Plane Plotter includes a series of Networking Test functions under the Help menu.  You will find these most helpful in checking out your system prior to applying for Ground Station or Master User status.


Why do I see someone else's share code as well as mine on the PlanePlotter Ground Station/Master User Test output page?


In response to this query Tim Plumridge said [edited]:


I was one of the earlier VM users to come across this problem; there were 4 PP

installations shown on my GS/MU test despite my portforwarding being correct.


An email to the group and Nic suggested the DNS workround which had helped in

earlier instances of VM (and other ISPs ? [including BT Internet]) 


I shall list the steps I used here to possibly help others. 


I use Windows 10, with latest updates all installed.


1) Control Panel

2) Network and Internet

3) Network and Sharing Centre - view Network status and tasks

4) Change adapter settings (on the left)

5) Right click on your wi-fi connection and click Properties

6) Click Internet Protocol Version 4 (TCP/IPv4) (you MAY need to scroll down)

and click Properties at the bottom

7) Under General tab click the option "Use the following DNS server addresses"

8) Alongside Preferred DNS server put

9) Alongside Alternate DNS server put

10) Press OK and close relevant windows


There MAY be shortcuts and / or different steps depending on Windows version;

try your GS/MU tests and redo the portforwarding if necessary. (For the Virgin

Superhub I find running the upnpmaster batch file within the PP installation

folder does the trick.)


As I say, the above worked for me and, thanks to Nic jogging my memory re the stuff, managed not to tear ALL of my hair out! 


Good luck





Why can't it be easier to set up as a Ground Station and Master User?


See: PC networking for Mlat


Comments (0)

You don't have permission to comment on this page.