I hadn't heard of that error before, so I looked it up and it sounds like a BSD thing.

Anyway, the problem is that you specified a listen queue size of 1, and somehow, that data device is sending packets faster than you receive and process them. The error will occur specifically when the device has sent one connection and you haven't accepted it yet and then receives another from the device. All you need to do is increase Listen => 1 to something bigger and you can buffer more incoming requests until you can get around to receiving them.

But, the problem might be in the code that handles them, or in a variety of other scenarios like if the socket doesn't cleanly close and leaves your end hanging waiting for more data on a socket that the device is no longer writing to. In addition to raising your Listen queue size, you should observe the timing of when you receive the message and when you finish processing it, i.e. by printing the current time at the end of your inner while loop.