Multicast Test On The Network

When you have servers in one cluster, the servers communicate with each other using multicast messaging mode. But a lot of times you see the messages in the log files of the servers like “Lost Multicast Messages”. This means there is something wrong in the servers communication. At this point of time it is necessary to test the network connection between the ip addresses where the clusters are running.

Syntax : java utils.MulticastTest -n name -a address [-p portnumber] [-t timeout] [-s send]

-N : Name of the server so that you can identify the communication.
-A : Multicast address on which the messages are sent and received.
-P : This is the multicast port number on which the servers communicate.
-T : This is the timeout value, if no multicase message is received within this time, warning is shown on the shell prompt.
-S : The duration in seconds between sending the messages.

Below is how you do it:

Test :  Start the command prompts on machines where you have your managed servers. (can be 1 or more)
Ensure that the servers in the cluster are not running, this test is for checking the network connectivity.

Set the java environment on both the shells. Then enter the below syntax:
System 1 : java utils.MulticastTest -N Server1 -A -P 7008 -T 10 -S 2
System 2 : java utils.MulticastTest -N Server2 -A -P 7008 -T 10 -S 2

Both servers will start sending and receiving messages as below:

Server 1 :

Server 2 :

The screen shots show that there is no issue in the connectivity. But when there is a lost message, it will show the message:

Received message 142 from Server1
Received message 134 from Server2
I (Server1) sent message num 143
Received message 143 from Server1
Missed message for Server2?  Last Seq 134 and just received 136
I (Server1) sent message num 144
Received message 144 from Server1
Received message 137 from Server2
I (Server1) sent message num 145
Received message 145 from Server1
Received message 138 from Server2
I (Server1) sent message num 146
Received message 146 from Server1
Received message 139 from Server2
Missed message for Server2?  Last Seq 139 and just received 141
I (Server1) sent message num 147
Received message 147 from Server1
Received message 142 from Server2
I (Server1) sent message num 148

This means message number 135 and 140 are lost by server2. In this situation, you know there is an issue. Check with the network administrator on what went wrong.

If you need any clarifications on the test, please do let us know.

Best Regards.

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