You seem to be transmitting fine:
monitoring=# select to_timestamp(timestamp) from stats where client_id = '6f67d3bf-d837-4fcb-b795-9987bd74d2c6' order by timestamp desc limit 10;
to_timestamp
------------------------
2015-12-24 16:14:34-05
2015-12-24 16:13:34-05
2015-12-24 16:12:34-05
2015-12-24 16:11:34-05
2015-12-24 16:10:34-05
2015-12-24 16:08:31-05
2015-12-24 16:07:31-05
2015-12-24 16:06:31-05
2015-12-24 16:05:31-05
2015-12-24 16:04:31-05
(10 rows)