Channelfinder-based name server for Channel Access? #2
Description
Looked at the CA server support that's included in CAJ. It's very easy to create the start of a "caSnooper" that logs all searches, but didn't find an obvious way to act as a name server, see comments in example:
import java.net.InetSocketAddress;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.Logger;
import gov.aps.jca.CAException;
import gov.aps.jca.CAStatus;
import gov.aps.jca.CAStatusException;
import gov.aps.jca.JCALibrary;
import gov.aps.jca.cas.ProcessVariable;
import gov.aps.jca.cas.ProcessVariableAttachCallback;
import gov.aps.jca.cas.ProcessVariableEventCallback;
import gov.aps.jca.cas.ProcessVariableExistanceCallback;
import gov.aps.jca.cas.ProcessVariableExistanceCompletion;
import gov.aps.jca.cas.Server;
import gov.aps.jca.cas.ServerContext;
public class CANameServer
{
public static void main(String[] args) throws Exception
{ // Log as much as possible
Logger logger = Logger.getLogger("");
logger.setLevel(Level.ALL);
for (Handler handler : logger.getHandlers())
handler.setLevel(Level.ALL);
JCALibrary jca = JCALibrary.getInstance();
Server server = new Server()
{
@Override
public ProcessVariableExistanceCompletion processVariableExistanceTest(String name,
InetSocketAddress client,
ProcessVariableExistanceCallback callback)
throws CAException, IllegalArgumentException, IllegalStateException
{
System.out.println("Client " + client + " searches for '" + name + "'");
// Options:
// 1) Return DOES_NOT_EXIST_HERE, and that's the end
// 2) Return EXISTS_HERE, in which case the library will reply with this server's IP and port,
// and then processVariableAttach() will be called to provide the PV
//
// There is no API for returning "EXISTS, but use the following IP and port",
// as necessary for a name server.
// The SearchResponse
// https://github.com/epics-base/jca/blob/master/src/core/com/cosylab/epics/caj/cas/handlers/SearchResponse.java
// always sends a reply with IP and port info from "context.getBroadcastTransport()".
//
// Need a CAS update which changes the ProcessVariableExistanceCompletion
// to allow something like
//
// return ProcessVariableExistanceCompletion.EXISTS(other_IP, other_port);
return ProcessVariableExistanceCompletion.EXISTS_HERE;
}
@Override
public ProcessVariable processVariableAttach(String name,
ProcessVariableEventCallback event,
ProcessVariableAttachCallback attach)
throws CAStatusException, IllegalArgumentException, IllegalStateException
{
throw new CAStatusException(CAStatus.NOSUPPORT, "not supported");
}
};
ServerContext context = jca.createServerContext(JCALibrary.CHANNEL_ACCESS_SERVER_JAVA, server);
context.run(0);
}
}
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