The LlpServer can be used to listen on a port and receive messages via LLP from many client hosts. Each host client connection is bi-directional allowing the receiving and sending of HL7 messages.

Two methods on the LlpServer class are of particular interest:

• startListen: Starts to listen on the given port for connections.
• stopListen: Stops listening on the current port for connections.

Event handlers are registered with the LlpServer to handle the asynchronous network events that will all be called back on the current thread. An event handler is written by the developer. The six main event handlers used for the LlpServer object are:

• clientConnected: Fired when a connection is made with the Listener.
• clientDisconnected: Fired when a client disconnects from the Listener, or a previous Disconnect call on a connection succeeds.
• clientErrorReceived: Fired when an error occurs with the TCP/IP connection.
• dataIgnored: Fired when received data is not within the header and trailer blocks.
• errorReceived: Fired when an error occurs with the Listener.
• messageReceived: Fired each time a message is received from a connected HL7 client.

Most of these events result in a discrete action regarding a specific connection. For this reason, most of these events pass an LlpConnection parameter. This parameter provides information about the client connection and methods to send messages back or disconnect from the client.

	Each instance of an LlpServer can listen to only one port at a time. If you need to listen to more than one port simultaneously, you will need to create one server instance for each port. LlpServer is designed to be a lightweight object so it is possible to instantiate multiple LlpServer instances without significant performance overhead. While you may need multiple LlpServer objects for the networking functionality, you would not need multiple Chameleon Engines to handle the HL7 functionality of your application.

For detailed information about the methods and events for the LlpServer class, consult the documentation for your language: