I'm trying to write a simple UDP transfer program in Labwindows/CVI. The idea is it creates 2 UDP channels, uses one to write data to a port, and the other to receive the data and print it out.
Here's the receiving end:
//Called whenever data arrives on port
int CVICALLBACK udpCallback(unsigned channel, int eventType, int errCode, void *callbackData)
{
printf("Callback called\n");
//Gets the data from port
readChannel();
return 0;
}
void createReadChannel()
{
//Channel for given port, receiving from any IP address
CreateUDPChannelConfig(port, UDP_ANY_ADDRESS, 0, NULL, NULL, &readerChannel);
//Attach callback to channel (above)
SetUDPAttribute(readerChannel, ATTR_UDP_CALLBACK, udpCallback);
printf("Read channel created\n");
}
My main problem is just that when I run it in debug mode, the shown callback function is never called, i.e. "Callback called" is not printed, not is any data stored or printed in the resulting readChannel() call.
However, when compiled and executed as an .exe, it works as intended. Every time data is received on that port the callback executes.
What difference could there be between the debug and 'release' version that would cause this to happen?
EDIT: After much testing I believe it has to do with waiting for messages using functions like getchar() which caused the main thread to hang up. Why it worked in release mode I don't know, but it probably has something to do with the difference in output window(?). My solution was to remove the callbacks and run the receiving channel on it's own thread.
This way the thread is always waiting for a message, using:
UDPRead(readerChannel, 0, 0, UDP_WAIT_FOREVER, NULL, NULL)) < 0)
And then my main thread can pick up messages as needed. If anyone has any additional info let me know.
