vPAR Transponder - Connections
March 1, 2005
Michael Oxner


The vPAR Transponder was meant to be as simple as practical for the pilot to use. As it stands, you have Flight Sim open, probably SquawkBox, a weather generating program, many with other nav programs or recording programs, Roger Wilco or AVC, and the list goes on. Why would you want yet another one open? Sorry. Has to be done.

Image 1 The program window on start up is meant to be pretty clean. The top left edit box is where you put you aircraft's callsign. It can be anything you like. If you're connected online with VatSim or other like service, it would be best if you use that callsign for continuity. Note that the window will force upper case, just like SquawkBox does. Whatever you type in here will be saved when you close the program.

The button to the right of the Ident box toggles the IP List Editor. More about that later.

The Tool Tips button just toggles the little hints that you see when you hover your cursor over a button or edit box. By default, they are off. We'll discuss the Editor button briefly later on this page, and in more depth on its own page. Normally, pilots will have no reason to open the Editor.

The Transponder has support for multiple connections. You can enter up to three Controller IP addresses and manage connections to each individually with the Connect button to the right of the associated IP edit box. This allows multiple PAR controllers to watch you. At big events or when PAR training is being conducted, you may be asked to link up to more than one controller. This was done in the past, so I understand, but it required opening more than one window of the Transponder. Now, it's all in one. When you connect to multiple controllers, they will all see the same callsign, since you can't change the callsign once you have one connection established.

There is now error checking for IP addresses to ensure it's a valid address. If the program finds an invalid address, it will report that in a message box when the Connect button is clicked. Only numeric addresses will work (125.48.96.252, vs. www.test.com, for example). If you want to connect to the QuadRadar running on your own machine, use the address reserved for the local machine 127.0.0.1, as seen in the screen shot here. The newest feature in the Transponder for Version 2.0, other than IP error checking, is the ability to save commonly used IP addresses in a dropdown list for each IP box. Ten addresses can be saved in these lists for convenience. For more on the IP List Editor, see the separate page on this feature listed in the index at left.

Click the Connect button for the line you have entered an IP, and it'll try to start. First off, if the Transponder can't read state data from Flight Sim, it won't even try to connect. Trying to connect when FS isn't running will fail it. When FS is "busy", like loading scenery if you've moved your aircraft by changing airports, it will fail. Note that if you're already connected and then FS pauses to load scenery, it will fail as well, and a counter begins to tally the failed read attempts. After a certain number of times (controlled by a value in the INI file), vPAR will disconnect. This counter resets to zero every time a successful read occurs. If it reads FS ok, it'll start the socket connect attempt. Typically this is a fast process. If it takes a long time to connect, the network path from you to your controller is probably very busy and a successful PAR is unlikely due to inadequate position update rates. If the connection fails, you should be presented with an error message giving the error code (like 10050, for example) in the status window. Due to limited space, limited explanation will be provided in this case, but many of the socket errors are so nondescript as to be practically useless for troubleshooting even with full descriptions. A successful connection to a PAR controller means good reading of FS state data and a reasonable socket connection to the controller, which will yield a message in the status box indicating data is being read and sent.

Image 3 Notice in this image that when you have a successful connection, the IP edit box and the callsign edit box are disabled. This is to prevent access to them so this information cannot be changed while connected. As long as any one of the three sockets is open, you won't be able to change your callsign. For each individual connection, as long as the socket associated with it is open, you won't be able to change the IP. This just makes sense, since you can't change an IP in the middle of a send, anyway. To change this stuff, simply disconnect, edit, and connect again. Also note that the Connect button has changed. It now shows that the next click will disconnect the socket, which will also stop reading FS state data if it's the last of the active connections to be closed.
 

Image 4 If you click the Disconnect button, it will simply close the associated connection between you and the PAR controller. The button will change to read "Connect", and the IP edit box will become enabled for editting again. You will also see in the status box a message indicating you have disconnected.

Another way to be disconnected, other than a socket error, is by the controller. The QuadRadar has a method of connection control built in. You may even be asked not to disconnect unless you're closing out altogether or it's causing problems for you, since the new QuadRadar has airport surface tracking abilities, too. If the controller disconnects you, you will see just the simple message above, that you are disconnected. It's a normal operation, so I didn't treat it specially when writing the code for it.

And that's it for a pilot's normal view of the Transponder. The only other issue that is practical for a pilot is the troubleshooting portion of the Editor. If you open the Editor while connected, you'll notice that the edit boxes associated with Latitude, Longitude and Elevation(more properly considered Altitude in this context) are updated with each interogation from the controller's Quad Radar. This will give you an idea of how often the position updates are being requested and sent. If it's much outside twice each second, the PAR's precision on final will be compromised. Once again, you'll probably have little reason to look here.