[HAPI-devel] Is there an equivalent to the Conectionlistener interface for a client connection?

[Martin D. <d3n...@ho...>]

First off, I would like to congratulate and thank each and every person who worked on the HAPI project, it is a phenomenally powerful library, awesome enough for me to decide to code a massive hospital ADT system around it.  My project is really 2 separate projects : a web project for users to interact with the database (create patients, orders, etc) and a standalone java app which is used as a connection / messaging service to different HL7 interfaces.  I am currently using the ConnectionListener interface for the usage (billing, inventory of a dispensing system) servers my service is running, something like this :

@Override
    public void connectionReceived(Connection theC)
    {
        connectionEntity.setStatus("Connected");
        connectionService.update(connectionEntity);

        logEntryService.logInfo(LogEntry.CONNECTIVITY, "Usage connection for " + intfc.getName() + "  received from " + theC.getRemoteAddress().toString());
    }

    @Override
    public void connectionDiscarded(Connection theC)
    {
        connectionEntity.setStatus("Listening");
        connectionService.update(connectionEntity);

        logEntryService.logWarning(LogEntry.CONNECTIVITY, "Lost usage connection for " + intfc.getName() + " from " + theC.getRemoteAddress().toString());
    }

This allows me to know, immediately, when a connection is established or lost and allows me to do all sorts of things in real time.  I also have a bunch of client connections and I was unable to find an equivalent interface to notify me when the server side of my client connections goes down.  I resorted to using monitor threads that check the result of the isOpen() method on my Connection objects every few seconds and, while it certainly does the trick, I was wondering if there was something more real time I could use.  I did try to implement ConnectionListener on my HL7ClientConnection objects but the connectionDiscarded method is not fired when the server side goes down.  In my IDE logs, I see the following being logged by HAPI when I stop the server my client connections are talking to :

2018-01-20 11:11:02.609  INFO 14536 --- [ hapi-worker-40] ca.uhn.hl7v2.llp.MllpDecoderState        : End of input stream reached.
2018-01-20 11:11:02.609  INFO 14536 --- [ hapi-worker-40] ca.uhn.hl7v2.llp.MllpDecoderState        : SocketException on read() attempt.  Socket appears to have been closed: End of input stream reached before message starts
2018-01-20 11:11:02.609  INFO 14536 --- [ hapi-worker-40] ca.uhn.hl7v2.app.Receiver                : SocketException: closing Connection from 192.168.0.175:2001, will no longer read messages with this Receiver: End of input stream reached before message starts
2018-01-20 11:11:30.582  INFO 14536 --- [nitoring Thread] ca.uhn.hl7v2.app.ConnectionHub           : Discarding connection which appears to be closed. Remote addr: /192.168.0.175

Can I somehow intercept / harness those exceptions in real time to avoid needing monitor threads?

Thanks!