To recreate:

1. Create a 3 node replica set (2 data nodes and 1 arbiter).
2. Start up an application using the mongodb driver with connections to the replica set.
3. Kill the primary
4. Allow the driver to detect that the primary is down
4. Start the primary again

Run netstat -a | grep CLOSE_WAIT. You should see that there are a couple connections left in the CLOSE_WAIT state for the server that had failed. In the case where a host is detected down, these connections should be closed.