CLI Magic: No-nonsense network

good introduction document.

Atop is a system and process manager that displays network traffic, along with other useful information such as CPU consumption, memory usage, and a process list. Atop has a handful of options to be passed to at startup. To see network network-related information and save it to a log file located in /var/log, start the application with atop -N > /var/log/atopnet.log.

Bmon is a bandwidth monitor for network connections. With it you can selectively watch a certain network card or a many of them, and even keep an eye on interfaces that are down (using the -a switch). Bmon can show results using either ASCII mode or the curses library, and can even generate statistics in an HTML file. If started without any options, bmon will show interface statistics using ncurses and display all available network connections. Once the application is started, you can press the g key to enable graphical mode and d to enable detailed statistics. If your server has subinterfaces, you can view them by pressing the f key.

Bwmon is similar to bmon, but it provides limited options. It shows bandwidth usage in curses mode and has options to show average bandwidth utilization since last boot (using -a), print maximum bandwidth utilization since the last launch of the program (using -m), and specify update timeout (using -u value).

Netwatch is an invaluable tool when it comes to network monitoring, and one of my personal favorites. It can not only show what IP addresses or hostnames are communicating with the outside, but also what ports they are using. Netwatch is great when you are a network administrator in a small or medium-sized office and your users are constantly downloading large files from the Internet. It can email you warnings about bandwidth usage (if you use the -u warnuser option) and can log all or specific packets.

Speedometer is a little different from the rest of these tools. It measures network traffic and the speed or progress of a certain file transfer. Let's say you want to see how fast someone can download a file from your server and how the download is going in real time. Enter speedometer filename, and the program will draw a progress bar that shows the speed of the transfer. It can print the RX and TX rates on a per-interface basis (using -rx iface and -tx iface). You can use speedometer to test the upstream speed of your ADSL line, the transfer speed of your LAN, or the time needed to send a file to a server.