Sends a packet.
If this JpcapSender instance was created by openDevice(), you need to set the Datalink layer's header (e.g., Ethernet header) of the packet.
If this JpcapSender instance was created by openRawSocket(), you can only send IP packets, but you may not need to set the Datalink layer's header of the IP packets you want to send.
Note: the implementation and behavior of a raw socket may vary in different OS. For example, in Windows 2000/XP, you need to manually set the datalink/IP headers of a packet.
@param packet Packet to be sent