Most hospitals will have what is called an interface engine. This is a piece of software which is responsible for accepting streams of HL7, queuing them and routing them to various hosts. There are a number of common interface engines deployed in the market. Names you will typically come across are:

• Cloverleaf
• STC Datagate (Seebeyond eGate)
• Neon (now owned by Sybase)
• Mitra PACS Broker

So to get a stream of HL7 data you will need to work with the administrator of one of these engines and get them to send a stream of HL7 data to you.