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Application for monitoring all applications that are using the internet in Mac OS X
I use Menu Meters to show me how much data is being sent and received by my Mac as a whole.
But (as far as I can tell), it doesn’t break it down by application. If there’s a lot of data being sent or received, it’d be nice to see which app is doing it.
Take a look at Little Snitch. It monitors which applications are using the network and also tracks usage. From its website:
Keep an eye on your traffic
Little Snitch 2 introduces a new Network Monitor, showing detailed information of all incoming and outgoing network traffic.
A status icon in the menu bar provides a summary of current network activity, and a monitor window with more comprehensive information pops up automatically in case of new traffic events.
There is the lsof terminal command. This has a size field (7th field by default). This has a plethora of switches. Can probably tell you all you need to know about data connections.
sudo lsof -i : this will give you a complete list of all open network connections. Does not appear to give you the amount of data written or read from each socket though.
When searching for well-known ports, such as 8080 which is listed as http-alt due to its mapping in /etc/services, it might be easier to use lsof -i -P to suppress conversion of port numbers to port names. Alternatively, explicitly specify the port one's looking for, like lsof -i tcp:8080. When just trying to figure out what services are actually listening, use lsof -i -P | grep LISTEN.
