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Oracle® Coherence Developer's Guide
Release 3.6.1

Part Number E15723-03
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43 Performing a Multicast Connectivity Test

Included with Coherence is a Multicast Test utility, which helps you determine if multicast is enabled between two or more computers. This is a connectivity test, not a load test, each instance will by default only transmit a single multicast packet once every two seconds. For network load testing, see Chapter 44, "Performing a Datagram Test for Network Performance."

Running the Multicast Test Utility

The Multicast Test utility supports a large number of configuration options, though only a few are required for basic operation. To run the Multicast Test utility use the following syntax from the command line:

java com.tangosol.net.MulticastTest <command value> <command value> ...

Table 43-1 describes the available command line options for the Multicast Test utility.

Table 43-1 Command Line Options for the Multicast Test Utility

Command Required/Optional Description Default

-local

Optional

The address of the NIC to transmit on, specified as an IP address

localhost

-group

Optional

The multicast address to use, specified as IP:port.

237.0.0.1:9000

-ttl

Optional

The time to live for multicast packets.

4

-delay

Optional

The delay between transmitting packets, specified in seconds.

2

-display

Optional

The number of bytes to display from unexpected packets.

0


Sample Commands

java com.tangosol.net.MulticastTest -group 237.0.0.1:9000

For ease of use, multicast-test.sh and multicast-test.cmd scripts are provided in the Coherence bin directory, and can be used to execute this test.

Note: before Coherence 3.1 the following syntax was used, and scripts were not provided:

java com.tangosol.net.MulticastTest <ip-addr> <multicast-addr> <port> <ttl> <delay-secs>

Multicast Test Example

Presume that you want to test if you can use multicast address 237.0.0.1, port 9000 (the test's defaults) to send messages between two servers: Server A with IP address 195.0.0.1 and Server B with IP address 195.0.0.2.

Starting with Server A, let's determine if it has multicast address 237.0.0.1 port 9000 available for 195.0.0.1 by first checking the machine or interface by itself as follows:

From a command prompt, enter the following command:

Example 43-1 Command to Determine a Multicast Address

multicast-test.sh -ttl 0

After pressing ENTER, you should see the Multicast Test utility display how it is sending sequential multicast packets and receiving them. Example 43-2 illustrates sample output.

Example 43-2 Sequential Multicast Packets Sent by the Multicast Test Utility

Starting test on ip=servera/195.0.0.1, group=/237.0.0.1:9000,ttl=0
Configuring multicast socket...
Starting listener...
Tue Mar 17 15:59:51 EST 2008: Sent packet 1.
Tue Mar 17 15:59:51 EST 2008: Received test packet 1 from self.
Tue Mar 17 15:59:53 EST 2008: Sent packet 2.
Tue Mar 17 15:59:53 EST 2008: Received test packet 2 from self.
...

When you have seen several these packets sent and received successfully, you can press CTRL-C to stop further testing.

If you do not see something similar to the above, then multicast is not working. Also, please note that we specified a TTL of 0 to prevent the multicast packets from leaving Server A.

You can repeat the same test on Server B to assure that it too has the multicast enabled for it's port combination.

Now to test multicast communications between Server A and Server B. For this test we will use a nonzero TTL which will allow the packets to leave their respective servers. By default the test will use a TTL of 4, if you believe that there may be more network hops required to route packets between Server A and Server B, you may specify a higher TTL value.

Start the test on Server A and Server B by entering the following command into the command windows and pressing ENTER:

multicast-test.sh

You should see something like the following on Server A:

Example 43-3 Sample Multicast Test Results from Server A

Starting test on ip=servera/195.0.0.1, group=/237.0.0.1:9000, ttl=4
Configuring multicast socket...
Starting listener...
Tue Mar 17 16:11:03 EST 2008: Sent packet 1.
Tue Mar 17 16:11:03 EST 2008: Received test packet 1 from self.
Tue Mar 17 16:11:05 EST 2008: Sent packet 2.
Tue Mar 17 16:11:05 EST 2008: Received test packet 2 from self.
Tue Mar 17 16:11:07 EST 2008: Sent packet 3.
Tue Mar 17 16:11:07 EST 2008: Received test packet 3 from self.
Tue Mar 17 16:11:09 EST 2008: Sent packet 4.
Tue Mar 17 16:11:09 EST 2008: Received test packet 4 from self.
Tue Mar 17 16:11:10 EST 2008: Received test packet 1 from ip=serverb/195.0.0.2, group=/237.0.0.1:9000, ttl=4.
Tue Mar 17 16:11:11 EST 2008: Sent packet 5.
Tue Mar 17 16:11:11 EST 2008: Received test packet 5 from self.
Tue Mar 17 16:11:12 EST 2008: Received test packet 2 from ip=serverb/195.0.0.2, group=/237.0.0.1:9000, ttl=4.
Tue Mar 17 16:11:13 EST 2008: Sent packet 6.
Tue Mar 17 16:11:13 EST 2008: Received test packet 6 from self.
Tue Mar 17 16:11:14 EST 2008: Received test packet 3 from ip=serverb/195.0.0.2, group=/237.0.0.1:9000, ttl=4.
Tue Mar 17 16:11:15 EST 2008: Sent packet 7.
Tue Mar 17 16:11:15 EST 2008: Received test packet 7 from self.
...

and something like the following on Server B:

Example 43-4 Sample Multicast Test Results on Server B

Starting test on ip=serverb/195.0.0.2, group=/237.0.0.1:9000, ttl=4
Configuring multicast socket...
Starting listener...
Tue Mar 17 16:11:10 EST 2008: Sent packet 1.
Tue Mar 17 16:11:10 EST 2008: Received test packet 1 from self.
Tue Mar 17 16:11:11 EST 2008: Received test packet 5 from ip=servera/195.0.0.1, group=/237.0.0.1:9000, ttl=4.
Tue Mar 17 16:11:12 EST 2008: Sent packet 2.
Tue Mar 17 16:11:12 EST 2008: Received test packet 2 from self.
Tue Mar 17 16:11:13 EST 2008: Received test packet 6 from ip=servera/195.0.0.1, group=/237.0.0.1:9000, ttl=4.
Tue Mar 17 16:11:14 EST 2008: Sent packet 3.
Tue Mar 17 16:11:14 EST 2008: Received test packet 3 from self.
Tue Mar 17 16:11:15 EST 2008: Received test packet 7 from ip=servera/195.0.0.1, group=/237.0.0.1:9000, ttl=4.
...

You can see that both Server A and Server B are issuing multicast packets and seeing their own and each other's packets. This indicates that multicast is functioning properly between these servers using the default multicast address and port.

Note: Server A sees only its own packets 1-4 until we start Server B and it receives packet 1 from Server B.

Troubleshooting Multicast Communications

If you are unable to establish bidirectional multicast communication please try the following:

If multicast is not functioning properly, you will need to consult with your network administrator or sysadmin to determine the cause and to correct the situation.