Listen if the TCP connection between robot and LV GUI is lost

Question

Hi
I'm doing a simple client/server TCP connection between a Labview GUI and a robot controller.
My robot controller acts as the TCP server that waits for a connection from the Labview GUI, it gets a string as a ready signal and then writes a string back to the LV GUI to tell that the controller is ready, then the LV GUI should be ready to send commands to the robot.
So now first of all there are two things I want to do;
1) I want the user to push a button to connect to the robot and then make a red/green light turn on if the connection is established, then the LV GUI also starts a small loop that waits fro whatever is coming from the robotcontroller, this is only for debugging right now
2) Secondly I want the LV GUI to listen if the connection somehow is lost, like if the robot goes out of range or some other programming error in the script for the robot controller that might make the TCP connection terminate. So if the connection is lost from the serverside, then I want the LV GUI to keep runing but just turn the light red.
I have tried some of the examples in Labview but I sure could need some help on this.
LV 8.5
LabVIEW 8.6 / 2009 / 2010
Vision Development Module 8.6 / 2009 / 2010
VBAI 3.6 / 2010
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Answer 1

You really should change your architecture. I assume that your other controls also control the robot, so you will need more complex messaging.
I suggest you look at some of the examples and templates for queued message handler. Essentially, this will allow you to send message between two loops, which is probably what you want.
As for what your comm loop should actually look like, you should separate the opening part from the communicating and closing part. That way, you can send the Ready string immediately after connecting. The example code you used already handles the timeout error, which is the indication you want that the connection was lost.
Here's one (very bad) example of how this could be done:
You should note that this does not really do any error handling. If you use a queued message handler and actually turn the comm loop into a state machine (with states like Open,Comm and Close), it should be cleaner.
To learn more about LabVIEW, I suggest you try looking at some of these tutorials.
Message Edited by tst on 01-19-2008 07:53 PM
Try to take over the world!
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