Java Communication API

Java communication API is a software module (library) allowing Java application talk through serial port.

Java comm is a must for serial and parallel port support because Java "Virtual Machine" doesn't offer such a capability itself.
Instead, Sun made an extension (javax.comm.*) module and offered it for download, for Solaris/SPARC and Windows platforms only. No Linux, Mac OS, OS/2 support.

So, people started to write their own communication libraries. Most of it works as "plug-ins" for original Sun package and are compatible with applications written for that API.

On this page you'll find some info about various comm packages for Java. You can use them for your own software or for existing one, like gar2rnx / Java.

Java comm packages:

• Sun's original site, http://java.sun.com/products/javacomm. Versions for Windows and Solaris plus documentation.
• RXTX site, http://www.rxtx.org offers open, free (GPL) and robust implementation of javax.comm plug-in and also complete rewrite, in gnu.io.* package. Versions for various UNIX platforms, Mac OS X, Win32, Windows CE and BeOS. You can download from here binary version for iPAQ.
• At Teilo.net there is a CEJavaComm package, free for non-commercial use. Version for Windows CE.
• ProSyst Developer Zone offers commercial package for Win32, Linux and Windows CE. 30 days free evaluation download.
• Solutions Consulting has Serialio.com - commercial package for many platforms.
• java.comm.MRJ is a driver for Mac MRJ (Macintosh Runtime for Java).

Installation notes:

I assume you're trying to use some kind of nonstandard configuration here. If you have standard PC with Windows and Sun Java Virtual Machine - just follow instructions for Sun package.

First, you should figure out whether package you downloaded works as Sun's package plug-in or as independent package.

If it works as a plug-in, you have to download original Sun package (most probably Solaris, not Windows version, but you should check your driver instruction for that).
Then, install Sun package by putting it's 3 files in three directories:

• Java JAR file should be put in your CLASSPATH.
  In Java 2 you just put it in .../jre/lib/ext/ directory and that's all.
  In Java 1.1.x machine (which is more common on "nonstandard" systems like palmtops, intelligent phones and so on) you have to put path to that file into CLASSPATH environment variable or put that path in command line, ie:
  • For Microsoft Virtual Machine built-in into every Windows before XP:

  jview /cp c:\windows\java\comm.jar;c:\other\classes\ ...

  • For Insignia Jeode Virtual Machine, available for Palmtops and other appliances:

  \windows\evm.exe -cp \windows\lib\comm.jar;\other\classes ...

  • For Sun, IBM, Oracle, Blackdown and many others old JRE ver 1.1.x:

  jre -cp /usr/local/java/lib/comm.jar -cp /other/class ...

  • For Macintosh Runtime for Java (MRJ) - I have no idea
• Native library (*.DLL or *.so) should be put into some place visible to system:
  • On MS Windows platforms (including Windows CE) it can be \windows or \winnt
  • On Unix it is sometimes /shlib or you set environment variable like LD_LIBRARY_PATH (which has many drawbacks - don't do it if you don't have to)
  • On Linux you put path to your library into /etc/ld.so.conf file and (important) then run ldconfig command which compiles this file and creates its binary version which is used by system.
  • On Macintosh - I have no idea
• Properties file (*.properties) have to be put in Java "lib" library:
• On Microsoft VM it should be put in Windows\java\lib directory. If there's no "lib" directory there - create it.
• On JRE or JDK 1.1.x, 1.2.x, 1.3.x, 1.4.x it should be put in java/jre/lib directory. In JDK it shouldn't be put in jdk_xxx/lib, but in jdk_xxx/jre/lib directory
• On MRJ - I have no idea
After you put properties file in correct location you should edit it so that it points to correct class name of your serial driver "plugin".

If your serial package works as package independent from Sun comm library, you should install it accordingly to instructions and remove Sun package from your system.
You should check whether your package implements standard javax.comm package like Sun. It can implement some other. For example, RXTX version 1.5 (currently in beta) implements "gnu.io" instead of "javax.comm". So you have to change your application source code, from "import javax.comm.*" to "import gnu.io.*"

Return to gar2rnx / Java homepage

Official address of this page: http://www.mhobot.w.pl/java/comm/

For questions and fixes mail to MichalHobot(at)netscape.net