Issues with retrieving NetworkTables

Technical Java
1

When we try to retrieve NetworkTables our driver station code crashes with the error:

Unhandled exception: java.lang.IllegalStateException: Network tables has already been initialized

The code on the coprocessor is:


NetworkTable.setIPAddress("59.40");
NetworkTable table = NetworkTable.getTable("Vision");
table.putNumber("Test Value", 8);

Then the code on the driver station is:


NetworkTable.setClientMode();
NetworkTable.setIPAddress("59.40");
table = NetworkTable.getTable("Vision");
SmartDashboard.putNumber("Test Value", table.getNumber("Test Value", 0));

We think it has something to do with NetworkTable.setClientMode() because when we remove that line it doesn’t crash but we are not able to retrieve the number.

2

Remove the setIPAddress line on the robot, and make sure on the client you set the IP address to the mDNS address of the robot - roborio-5940-FRC.local.

3

I made the suggested changes and it still has the same error.

4

Are you calling the setClientMode/setIPAddress/getTable calls repeatedly? They should only be called once on robot initialization.

5

When we delete all of the lines of the robot code except for NetworkTables.setClientMode() it still crashes.

I am sure we are not calling it twice.

6

Just a quick update. On the coprocessor, I ran table.isConnected(), and it returned false.

7

I was able to fix the problem. NetworkTable.setServerMode() is automatically done in the robot code which causes the code to crash if you call NetworkTable.setClientMode().

I removed NetwokTable.setClientMode() from the robot code and put it on the coprocessor instead. I also moved NetworkTable.setIpAddress() to the coprocessor.