Let me try to explain you how data are transfered to different services, it will help you to understand why the buffer overflow happen and how to try to avoid them

You have a service (A) that publish data (in your case, the Arduino service that publish the pin value), so the data are put into the arduino outbox buffer. Then those data will be transfered to the inbox buffer of every services (B) that listening to those data (in your case, the serialGui). Service B will then take and remove one data from it's inbox and process it, then take another one and process it and so on.

Now what happen if service A publish data more quickly than service B can process them, the data will accumulate in the input buffer of service B. At some point, the input buffer will get full and the output buffer of service A will complain that he have no place to put the data, that's the error message you are seeing.

So sometimes it need to have some synchronization between the publisher service and the listener service to avoid the buffer to overflow.

So how to prevent the buffer overflow

• Have service A publish less data, it will gives more time for service B to process the data. (in your case you may try to lower the pin polling rate)
• Have service B process the data faster by optimizing code
• Have some code in service B that decide if it should process the data or discard them because it's not going fast enough (kind of a safety valve)

in your specific example, when you select text in the box, the serialGui seem to halt, no other data get processed and show in the GUI. So the input buffer get quickly full and you get the buffer overflow errors.

Not sure how to fix that specific case, but one thing that's i'm sure is that those buffer overflow have no consequence other than losing some data to show in the serialGui. If anothe service is listening to the publish data, it should receive the data normally just as the serialGui is working normally. So that's annoying, but your code should work normally