Code Excursion

Helpful Linux Commands for testing Multicasting

Finding useful commands for troubleshooting multicasting was difficult because most were not installed on the servers.

Running the following command should display number of incoming and outgoing multicast packets. Running it multiple times should result in the numbers increasing in value.

Display multicast packet counts

  $ netstat -sgu | grep Mcast

Display multicast ip addresses joined

  $ netstat -gn

Running ifconfig should display multicast in the resulting output. ifconfig

Display network interface information

  $ ifconfig
  eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
  ...stuff omitted...

Omping can be used to troubleshoot multicasting. When run on two different servers/VMs it uses multicasting and reports on packet losses when stopped with Ctrl-C.

Run omping

omping -m <multicast address> -p <multicast port> <This servers IP adddress> <Other servers IP address>

Show IP addresses and Ports that are listening.

Display listening ports

netstat -tulpn | grep LISTEN