I have 64bit Ubuntu 12.04, fresh install. I want to do this except every guide seems to fail to work. The standard package is javax.comm or gnu.io.* . The latter (possibly both) involves installing a rxtx library. I have the library in an archive but part of the installation step is putting the right files into my jre/.... folder, except I don't know which one because I have anywhere from 4 to 10 different directories within my /usr/lib/jvm/ directory, depending on which java packages I install using Synaptic (java-7-openjdk-amd64, java-6-openjdk-amd64,java-1.5.0-gcj-4.6,java-7-oracle, etc. Installed Netbeans makes it go from 2 to 8!!). I have a test java file which is to be run via 'javac TestFile.java' , such as the one here. The problem is that no matter what I've installed or which guide I've followed it immediately fails by complaining it can't find the rxtx library, be it the gnu.io.* or javax.comm. According to Synaptic I have version 2.2 of the rxtx.com library installed. I've tried installing Java by installing Netbeans or Eclipse or both, adding libraries, pointing to files, moving .jar files about. Nothing allows me to run ANY file which involves the com port libraries! I must have wasted 5 hours on it today. To give some context, I'm messing around with an Arduino Uno. I have installed the Arduino software via the Ubuntu manager and I can run it, upload programs and even use it to monitor the serial connection, correctly displaying the information I expect. But when I try to get Java to read the serial connection so I can do more elaborate things with the data, on a computer with a processor faster than 16MHz(!), and then send stuff back to the Arduino but I can't get Java to even build the program!! I have a book which is all about Arduino projects and it has a step by step guide to doing this in Python, which works, but I want to do it in Java due to the stuff I want to do with the data being already in Java. There's an Arduino/Eclipse IDE but Eclipse instantly crashes in 64bit Ubuntu 12.04. Fan-****ing-tastic. What I want is just to have a working connection and a simple java file which reads the serial connection and, for instance, prints it to screen. Once I've got that I can move on to more complicated things, but I can't even install the rxtx library for Java! Please, if anyone knows the sequence of commands to set up Ubuntu so this file or even something which is just 'import javax.comm' works when you do 'javac File.java' I would be extremely grateful. I'm currently a Java novice and part of the reason for doing this is to have a fun way of getting into Java. Currently all it makes me want to do is punch the person who wrote the rxtx library for making it so bloody convoluted to install!