comm_poll_incoming: NULL write handler

What does the following mean in the cache log, I see it all the time.

1999/06/26 00:03:17| comm_poll_incoming: NULL write handler
1999/06/26 00:03:17| comm_poll_incoming: NULL write handler
1999/06/26 00:03:17| comm_poll_incoming: NULL write handler
1999/06/26 00:03:17| comm_poll_incoming: NULL write handler
1999/06/26 00:03:17| comm_poll_incoming: NULL write handler
1999/06/26 00:03:17| comm_poll_incoming: NULL write handler

2.2STABLE3

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Brian Feeny (BF304) signal@shreve.net
318-222-2638 x 109 http://www.shreve.net/~signal
Network Administrator ShreveNet Inc. (ASN 11881)
Received on Sat Jun 26 1999 - 14:42:39 MDT