Digi XB3-C-A2-UT series User Manual page 86

Sleep modes
socket.send raises OSError: ENOTCONN
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socket.sendto raises OSError: ENOTCONN
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socket.recv returns the empty string, the traditional end-of-file return value
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socket.recvfrom returns an empty message, for example:
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(b'', (<address from connect()>, <port from connect()>) )
The underlying UDP socket resources have been released at this point.
Digi XBee3 Cellular LTE-M Global Smart Modem User Guide
MicroPython sleep behavior
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