I have a Java client which monitors RabbitMQ queue. I am able to get the count of messages currently in queue with this code
@Resource RabbitAdmin rabbitAdmi
To access queue details via http api,
http://public-domain-name:15672/api/queues/%2f/queue_name
To access queue details via command from localhost cli promt,
curl -i -u guest_uname:guest_password http://localhost:15672/api/queues/%2f/queue_name
Where, %2f is default vhost "/"