pip install pcapy error : Cannot open include file: 'pcap.h'

1. Download the WinPcap Developer's Pack.
2. Use pip's --global-option. setup.py is different, but I think pip is preferred over setup.py anyway. Here's an example line (substitute in the correct paths for your system; I just referenced them right in the Downloads folder):
   

   pip install pcapy --global-option=build_ext --global-option="-LC:\path\to\WpdPack_4_1_2\WpdPack\Lib" --global-option="-IC:\path\to\WpdPack_4_1_2\WpdPack\Include