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You can tell if the local card is active or not simply by looking at the output of the "ifconfig" command (if the interface isn't listed, it isn't up).
If you want to check a remote device, then your only choice is to ping it since you need to make some contact to determine if the other device is listening or not. However, you can check if you are connected to an active network passively by using tcpdump. If you are connected to a live network, tcpdump will show any packets that drift by your machine. Though, due to the nature of switched networks, it might appear that very little is going on.
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