Update TODO.txt

TODO.txt

@@ -1,19 +1,23 @@
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+# improvement:
 # adapt code to fulfill PEP 8
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+# improvement:
 # replace print() with logging.info(), logging.warning() and logging.error() as it corresponds
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+# new feature:
 # show other connection states, in addition to ESTABLISHED:
 # states: LISTEN, SYN-SENT, SYN-RECEIVED, ESTABLISHED, FIN-WAIT-1, FIN-WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK,
   TIME-WAIT, and the fictional state CLOSED
 # RFC 739: https://datatracker.ietf.org/doc/html/rfc793
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+# improvement:
 # use rx_kB and tx_kB instead of rx and tx in nodes
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