Java中的COM端口标识

Question

I use the following code to identify the comports. In my system there are three ports but it is showing false in ports.hasMoreElements() method. I also added comm.jar in the library and i am using windows xp (service pack 3). Kindly look into the code and help me.

import java.util.*;
import javax.comm.*;

public class Main
{
    public static void main(String[] args)
    {
        Enumeration ports = CommPortIdentifier.getPortIdentifiers();
        System.out.println(ports.hasMoreElements());
        while(ports.hasMoreElements())
        {
            CommPortIdentifier cpi =
                           (CommPortIdentifier)ports.nextElement();
            System.out.println("Port " + cpi.getName());
        }
    }
}

Thanks in advance..

Answer 1

you just import "import gnu.io.*;" and RxTxcomm.jar add into libraries.

1) Download Rxtx binaries from http://rxtx.qbang.org/wiki/index.php/Download
2) Extract the zip file.
3) Copy RXTXcomm.jar ---> <JAVA_HOME>/jre/lib/ext
4) Copy librxtxSerial.so ---> <JAVA_HOME>/jre/lib/i386/
5) Copy librxtxParallel.so ---> <JAVA_HOME>/jre/lib/i386/

Answer 2

There are some tricks involved in getting the Java Communications API to correctly interact with the Windows system. Among the items that you download from Sun are three very important files:

comm.jar  
win32com.dll  
javax.comm.properties  

For the JVM to recognize the serial ports, proper placement of these files is important.

Use the following installation methods to be effective:
comm.jar should be placed in:

%JAVA_HOME%/lib  
%JAVA_HOME%/jre/lib/ext    

win32com.dll should be placed in:

%JAVA_HOME%/bin   
%JAVA_HOME%/jre/bin  
%windir%System32  

javax.comm.properties should be placed in:

%JAVA_HOME%/lib  
%JAVA_HOME%/jre/lib

Answer 3

Thats THE prototypical problem with the commapi :-)

Read through the installation guide, beside javacomm.api or wossname, two or three other files have to be copied to a very specific location.

All of them.

Otherwise you simply don't see any com ports, error handling's a bit on the weak side, sorry, I went through the same thing about thrice myself ;-)

Answer 4

%JAVA_HOME%/lib  
%JAVA_HOME%/jre/lib/ext    

win32com.dll should be placed in:

%JAVA_HOME%/bin   
%JAVA_HOME%/jre/bin  
%windir%System32  

javax.comm.properties should be placed in:

%JAVA_HOME%/lib  
%JAVA_HOME%/jre/lib  //this work out for me by sann seun

Answer 5

comm.jar should be placed in:

%JAVA_HOME%/lib  
%JAVA_HOME%/jre/lib/ext 

win32com.dll should be placed in:

%JAVA_HOME%/bin   
%JAVA_HOME%/jre/bin  
%windir%System32

javax.comm.properties should be placed in:

%JAVA_HOME%/lib  
%JAVA_HOME%/jre/lib  //this work out for me by sanni seun