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Listing Comm ports on WinXP SP2

Posted on 2006-07-03
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Last Modified: 2010-05-18
Hi,

I have the following code from the book Java I/O:

import javax.comm.*;
public class NamedPortLister {
  public static void main(String[] args) {
    // List serial (COM) ports.
    try {
      int portNumber = 1;
      while (true) {
        CommPortIdentifier.getPortIdentifier("COM" + portNumber);
        System.out.println("COM" + portNumber);
        portNumber++;
      }

    }
    catch (NoSuchPortException ex) {
      // Break out of loop.
    }
    // List parallel (LPT) ports.
    try {
      int portNumber = 1;
      while (true) {
        CommPortIdentifier.getPortIdentifier("LPT" + portNumber);
        System.out.println("LPT" + portNumber);
        portNumber++;
      }
    }
    catch (NoSuchPortException ex) {
      // Break out of loop.
    }
  }
}

I have tried Netbeans & the command line. Both compile and *seem* to run, however there is no output??
Running WinXp SP2
Java Comm 2.0
JDK 1.5.07

Cheers,
Craig
0
Comment
Question by:cbumpste
  • 5
  • 3
  • 2
  • +1
11 Comments
 
LVL 14

Expert Comment

by:Tommy Braas
ID: 17029443
You are probably getting an exception, which you are ignoring. Ignoring as VERY BAD practice!

Add a:
ex.printStackTrace();
to each catch to see what is going on
0
 
LVL 14

Expert Comment

by:Tommy Braas
ID: 17029449
'as' in the above should be 'is'... :-)

Such that:
Ignoring exceptions is VERY BAD practice!
0
 
LVL 35

Expert Comment

by:girionis
ID: 17029452
Try to code the catch block, it might be going in there, i.e. not finding any port. Change this

>  catch (NoSuchPortException ex) {
>       // Break out of loop.
>     }

to

catch (NoSuchPortException ex) {
     System.out.println("Exception: " + ex);
    }

and see if you get any error messages.
0
 
LVL 92

Expert Comment

by:objects
ID: 17029494
make sure you corectly installed the javacomm dll and properties file as per the install document.
0
 
LVL 35

Expert Comment

by:girionis
ID: 17029502
And make sure the javax.comm.properties is in the correct place (<jdk>/lib), otherwise have a look in the installation instructions for alternative locations.
0
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LVL 35

Expert Comment

by:girionis
ID: 17029506
Bah... objects was faster.
0
 

Author Comment

by:cbumpste
ID: 17029575
Thanks guys,

I added the exception that you suggested. I got the following:


javax.comm.NoSuchPortException
        at javax.comm.CommPortIdentifier.getPortIdentifier(CommPortIdentifier.java:105)
        at NamedPortLister.main(NamedPortLister.java:8)
Exception: javax.comm.NoSuchPortException
Exception: javax.comm.NoSuchPortException

No such port? I have a physical port on my laptop.
I have Administrator rights on the box.

Cheers,
Craig
0
 
LVL 35

Accepted Solution

by:
girionis earned 125 total points
ID: 17029610
Try the following:

1) Copy the javax.comm.properties into your $JAVA_HOME/jre/lib folder
2) copy the win32com.dll into your $JAVA_HOME/bin

and try again.
0
 

Author Comment

by:cbumpste
ID: 17029643
girionis,

The jre directory under the jdk directory was missing those files. Bugger!

Thanks again everyone!!!
0
 
LVL 35

Expert Comment

by:girionis
ID: 17029656
:)
0
 

Author Comment

by:cbumpste
ID: 17029658
Guys,

Sorry that it appears that only a single person can be assigned points.

The tips on the printing exceptions were good as well.

Cheers,
Craig
0

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