NetSpeedMonitor is not available for Linux but there are a few alternatives that runs on Linux with similar functionality. The best Linux alternative is BitMeter OS, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to NetSpeedMonitor and three of them are available for Linux so hopefully you can find a suitable replacement. Other interesting Linux alternatives to NetSpeedMonitor are Smart Traffic Meter (Free, Open Source) and Netspeed (Free, Open Source).
Smart Traffic Meter is a Linux network usage monitor. The program shows real-time graphs and reports. Smart Traffic Meter runs as a system daemon and displays all information in a web user interface accessible through a web browser.