Question: how to install rxtx on linux?
Answer: unpack the archive: rxtx-*-linux.zip,
copy librxtxSerial.so to %JAVA_HOME%/jre/lib/i386, (%JAVA_HOME% is the folder where JRE is installed on your system; e.g. /usr/local/j2sdk1.4.1_01)
copy RXTXcomm.jar to %JAVA_HOME%/jre/lib/ext.