Java IO.pdf - Nguyen Dang Binh

Java I/O
The name argument is a name for the program that wants to use the port and will be returned
by getCurrentOwner() while the port is in use. The timeout argument is the maximum
number of milliseconds this method will block while waiting for the port to become available.
If the operation does not complete within that time, a PortInUseException is thrown.
Example 17.4 is a variation of the PortLister program that attempts to open each unowned
port.
Example 17.4. PortOpener
import javax.comm.*;
import java.util.*;
public class PortOpener {
}
public static void main(String[] args) {
}
Enumeration thePorts = CommPortIdentifier.getPortIdentifiers();
while (thePorts.hasMoreElements()) {
CommPortIdentifier com = (CommPortIdentifier) thePorts.nextElement();
System.out.print(com.getName());
}
switch(com.getPortType()) {
case CommPortIdentifier.PORT_SERIAL:
System.out.print(", a serial port, ");
break;
case CommPortIdentifier.PORT_PARALLEL:
System.out.print(", a parallel port, ");
break;
default:
// important since other types of ports like USB
// and firewire are expected to be added in the future
System.out.print(" , a port of unknown type, ");
break;
}
try {
CommPort thePort = com.open("PortOpener", 10);
System.out.println("is not currently owned.");
thePort.close();
}
catch (PortInUseException e) {
String owner = com.getCurrentOwner();
if (owner == null) owner = "unknown";
System.out.println("is currently owned by " + owner + ".");
}
Here's the output:
D:\JAVA\16>java PortOpener
COM1, a serial port, is not currently owned.
COM2, a serial port, is currently owned by Port currently not owned.
LPT1, a parallel port, is not currently owned.
LPT2, a parallel port, is currently owned by Port currently not owned.
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