Nethogs is the tool to monitor the processes that are using internet and it also specifies how much bandwidth (speed in KB/sec) i.e. how much data is sent and how much is received.
Install nethogs using command:
If you are using wireless connection, then specify the device like:
I found the process “java” was eating up bandwidth and I killed the process using command:
Then you may again execute nethogs command to see if it’s gone or not.