Java IO.pdf - Nguyen Dang Binh

CommPortOwnershipListener.PORT_OWNED
CommPortOwnershipListener.PORT_UNOWNED
CommPortOwnershipListener.PORT_OWNERSHIP_REQUESTED
Java I/O
PORT_OWNED means some application has taken ownership of the port. PORT_UNOWNED means
some application has released ownership of the port. Finally, PORT_OWNERSHIP_REQUESTED
means some application has requested ownership of the port but does not yet have it, because
another application owns it. If the owner of the port hears the event, it can close the port to
give it up to the requesting application. Example 17.5 is a program that watches for port
ownership changes. It's of limited use, since these events only appear to be fired when a Java
program takes over or releases a port, not when other programs do.
Example 17.5. PortWatcher
import javax.comm.*;
public class PortWatcher implements CommPortOwnershipListener {
String portName;
public PortWatcher(String portName) throws NoSuchPortException {
this.portName = portName;
CommPortIdentifier portIdentifier =
CommPortIdentifier.getPortIdentifier(portName);
portIdentifier.addPortOwnershipListener(this);
}
public void ownershipChange(int type) {
}
}
}
switch (type) {
}
case CommPortOwnershipListener.PORT_OWNED:
System.out.println(portName + " has become unavailable");
break;
case CommPortOwnershipListener.PORT_UNOWNED:
System.out.println(portName + " has become available");
break;
case CommPortOwnershipListener.PORT_OWNERSHIP_REQUESTED:
System.out.println("An application has requested onwership of "
+ portName);
break;
default:
System.out.println("Unknown port ownership event, type " + type);
public static void main(String[] args) {
try {
PortWatcher pw = new PortWatcher(args[0]);
}
catch (Exception e) {
System.err.println("Usage: java PortWatcher port_name");
}
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