# Installation Instructions for JGroups

JGroups comes in a binary and a source version: the binary version is JGroups-2.x.x.bin.zip, the source version is JGroups-2.x.x.src.zip . The binary version contains the JGroups JAR file, plus a number of JARs needed by JGroups. The source version contains all source files, plus several JAR files needed by JGroups, e.g. ANT to build JGroups from source.

### Requirements

- JGroups 2.2.8 has a version that runs on JDK 1.3, and one that requires 1.4 or higher.
- From JGroups 2.2.9 on, the required JDK is 1.4 or higher. There is no JNI code present so it should run on all platforms.
- An XML parser is required for configuration of JGroups if you want the ability to use XML configuration files for class mapping, and to read protocol stack specifications in XML format. Not using an XML parser will result in slower serialization and limit you to use only plain protocol stack configuration strings. Note that any other JAXP compliant XML parser can be used. This is only relevant for JDK 1.3; higher JDKs come with an XML parser.
- If you want to generate HTML-based test reports from the unittests, then xalan.jar needs to be in the CLASSPATH (also available in the lib directory)

### Installing the binary distribution

The binary version contains

1. jgroups-all.jar: the JGroups library including the demos
2. CREDITS: list of contributors
3. INSTALL.html: this file
4. commons-logging.jar
5. concurrent.jar
6. log4j.jar

We no longer ship the Xerces JARs. To run JGroups you have to have an XML parser installed on your system. If you use JDK 1.4, you can use the parser that is shipped with it.
Place the JAR files somewhere in your CLASSPATH, and you're ready to start using JGroups. If you already have Xerces installed, or if you have another XML parser, the Xerces JARs can be omitted.
If you want to use the JGroups JMS protocol (org.jgroups.protocols.JMS), then you will also need to place jms.jar somewhere in your CLASSPATH.

### Installing the source distribution

The source version consists of the following directories:

1. src: the sources
2. test: unit and stress tests
3. conf: configuration files needed by JGroups, plus default protocol stack definitions
4. doc: documentation
5. lib: various JARs needed to build and run JGroups:

1. Ant JARs: used to build JGroups. If you already have Ant installed, you won't need these files
2. jms.jar: JMS library. Needed if you intend to run the org.jgroups.protocols.JMS protocol
3. junit.jar: to run the JUnit test cases
4. xalan.jar : to format the output of the JUnit tests using an XSLT converter to HTML
5. concurrent.jar
6. commons-logging.jar
7. log4j.jar
8. etc

### Building JGroups (source distribution only)

1. Unzip the source distribution, e.g. unzip JGroups-2.x.x.src.zip. This will create the JGroups-2.x.x directory (root directory) under the current directory.
2. cd to the root directory
3. Modify build.properties if you want to use a Java compiler other than javac (e.g. jikes)
4. On UNIX systems use `build.sh`, on Windows `build.bat: $> ./build.sh compile`
5. This will compile all Java files (into the `classes` directory).
6. To generate the JARs: `$> ./build.sh jar`
7. This will generate the following JAR files in the `dist` directory:
   - `jgroups-core.jar` - the core JGroups libraries
   - `jgroups-all.jar` - the complete JGroups libraries including demos and unit tests
8. The CLASSPATH now has to be set accordingly: the following directories and/or JARs have to be included:

1. <JGroups rootdir>/classes
2. <JGroups rootdir>/conf
3. All needed JAR files in <JGroups rootdir>/lib. To build from sources, the two Ant JARs are required. To run unit tests, the JUnit (and possibly Xalan) JARs are needed.

9. To generate JavaDocs simple run $> ./`build.sh javadoc` and the Javadoc documentation will be generated in the `dist/javadoc` directory
10. Note that - if you already have Ant installed on your system - you do not need to use build.sh or build.bat, simply invoke ant on the build.xml file. To be able to invoked ant from any directory below the root directory, place ANT_ARGS="-find build.xml -emacs" into the .antrc file in yourhome directory.
11. For more details on Ant see http://jakarta.apache.org/ant/ .

### Testing your Setup

To see whether your system can find the JGroups classes, execute the following command:

    java org.jgroups.Version

or (from JGroups 2.2.8 on)
java -jar jgroups-all.jar
You should see the following output (more or less) if the class is found:

    Version:        2.2.8 RC1
    CVS:            $Id: INSTALL.html,v 1.6 2006/10/09 13:36:35 belaban Exp $
    History:        (see doc/history.txt for details)

### Running a Demo Program

To test whether JGroups works okay on your machine, run

    java org.jgroups.demos.Draw

twice. 2 whiteboard windows should appear. If you started them simultaneously, they should initially show a membership of 1 in their title bars. After some time, both windows should show 2. This means that the two instances found each other and formed a group.

When drawing in one window, the second instance should also be updated. As the default group transport uses IP multicast, make sure that - if you want to start the 2 instances in different subnets - IP multicast is enabled. If this is not the case, the 2 instances won't 'find' each other and the sample won't work.

You can change the properties of the demo to for example use a different transport if multicast doesn't work (it should always work on the same machine). Please consult the documentation to see how to do this.

### Using IP Multicasting without a network connection

Sometimes there isn't a network connection (e.g. DSL modem is down), or we want to multicast only on the local machine. For this the loopback interface (typically lo) can be configured, e.g.

    route add -net 224.0.0.0 netmask 224.0.0.0 dev lo

This means that all traffic directed to the 224.0.0.0 network will be sent to the loopback interface, which means it doesn't need any network to be running. Note that the 224.0.0.0 network is a placeholder for all multicast addresses in most UNIX implementations: it will catch all multicast traffic. This is an undocumented feature of /sbin/route and may not work across all UNIX flavors. The above instructions may also work for Windows systems, but this hasn't been tested. Note that not all systems allow multicast traffic to use the loopback interface.

Typical home networks have a gateway/firewall with 2 NICs: the first (eth0) is connected to the outside world (Internet Service Provider), the second (eth1) to the internal network, with the gateway firewalling/masquerading traffic between the internal and external networks. If no route for multicast traffic is added, the default will be to use the fdefault gateway, which will typically direct the multicast traffic towards the ISP. To prevent this (e.g. ISP drops multicast traffic, or latency is too high), we recommend to add a route for multicast traffic which goes to the internal network (e.g. eth1).

### It doesn't work !

Make sure your machine is set up correctly for IP multicast. There are 2 test programs that can be used to detect this: McastReceiverTest and McastSenderTest. Start McastReceiverTest, e.g.

    java org.jgroups.tests.McastReceiverTest -mcast_addr 224.10.10.10 -port 5555

Then start McastSenderTest:

    java org.jgroups.tests.McastSenderTest -mcast_addr 224.10.10.10 -port 5555

You should be able to type in the McastSenderTest window and see the output in the McastReceiverWindow. If not, try to use -ttl 32 in the sender. If this still fails, consult a system administrator to help you setup IP multicast correctly. If you are the system administrator, look for another job :-)

Other means of getting help: there is a public forum on JIRA for questions. Also consider subscribing to the javagroups-users mailing list to discuss such and other problems.

### The instances still don't find each other !

In this case we have to use a sledgehammer (running only under JDK 1.4. and higher): we can enable the above sender and receiver test to use all available interfaces for sending and receiving. One of them will certainly be the right one... Start the receiver as follows:

    java org.jgroups.tests.McastReceiverTest1_4 -mcast_addr 228.8.8.8 -use_all_interfaces

The multicast receiver uses the 1.4 functionality to list all available network interfaces and bind to all of them (including the loopback interface). This means that whichever interface a packet comes in on, we will receive it.
Now start the sender:

    java org.jgroups.tests.McastSenderTest1_4 -mcast_addr 228.8.8.8 -use_all_interfaces

###

The sender will also determine the available network interfaces and send each packet over all interfaces.

This test can be used to find out which network interface to bind to when previously no packets were received. E.g. when you see the following output in the receiver:

    bash-2.03$ java org.jgroups.tests.McastReceiverTest1_4 -mcast_addr 228.8.8.8 -bind_addr 192.168.168.4
    Socket=0.0.0.0/0.0.0.0:5555, bind interface=/192.168.168.4
    dd [sender=192.168.168.4:5555]
    dd [sender=192.168.168.1:5555]
    dd [sender=192.168.168.2:5555]

you know that you can bind to any of the 192.168.168.{1,2,4} interfaces to receive your multicast packets. In this case you would need to modify your protocol spec to include bind_addr=192.168.168.2 in UDP, e.g. "UDP(mcast_addr=228.8.8.8;bind_addr=192.168.168.2):..." .

Alternatively you can use McastDiscovery1_4 (runs only on JDK 1.4). Start this program simultaneously on multiple machines. Binding to all available interfaces, this program tries to discover what other members are available in a network and determines which interfaces should be used by UDP. After some time (e.g. 30 seconds), press <enter> on each program. The program will then list the interfaces which can be used to bind to. There may be one or multiple interfaces. When there are multiple interfaces listed, take the one with the highest number of responses (at the top of the list). The UDP protocol spec can then be changed to explicitly bind to that interface, e.g.

"UDP(bind_addr=<interface>;...)"

### Problems with IPv6

Another source of problems might be the use of IPv6, and/or misconfiguration of /etc/hosts. If you communicate between an IPv4 and an IPv6 host, and they are not able to find each other, try the java.net.preferIP4Stack=true property, e.g.

java -Djava.net.preferIPv4Stack=true org.jgroups.demos.Draw -props file:c:\\udp.xml

JDK 1.4.1 uses IPv6 by default, although is has a dual stack, that is, it also supports IPv4. Here's more details on the subject.

### I have discovered a bug !

If you think that you discovered a bug, submit a bug report on JIRA or send email to javagroups-developers if you're unsure about it. Please include the following information:

- Version of JGroups (j`ava org.jgroups.Version`)
- Platform (e.g. Solaris 8)
- Version of JDK (e.g. JDK 1.4.2_07)
- Stack trace. Use kill -3 PID on UNIX systems or CTRL-BREAK on windows machines
- Small program that reproduces the bug