Application requiring QoS

We have been working on a RHO elements application for the public safety industry. One thing we have come across is that we require QOS on our transactions to ensure that a message will arrive at a client for processing.  If not there are a number of mechanisms we use to ensure this, for example message retries is a simple one.

Do any of you guys know if there is an ability to layer some style of QOS on to an application using web sockets to connect to the backend. 

If you don’t know would you be able to point me in the right direction.