The command line interface is one where the interaction with OS is possible by the commands and instructions. No Graphical facility is available like drag and drop facility.

Learn how to program in GML or use the Drag&Drop interface.

For a message to send out, it has to address which Mac address to send. If the message I received doesn't not match with my MAC address then my network interface will drop the packet completely. If your network is on promiscuous mode, then your network interface will not drop the message. It is good for packet sniffing.

I hope this helps.

Yes. 10/100/1000 NICs can drop down to the lowest available speed.

Contact angle is the angle that a drop of liquid makes as it meets the surface or interface of another phase, usually a solid