The ISBN is 978-0-9799587-1-7 (ISBN-10 is 0-9799587-1-7)http://download.youkuaiyun.com/detail/jiajianjunneusoft/6987467

http://stackoverflow.com/questions/11668172/how-do-i-calculate-ip-header-lengthhttp://www.cnblogs.com/fhefh/archive/2011/10/19/2217954.html

Why nmap -PU can't find any host available,even the target machine return an ICMP port unreachable packet.I run [nmap -sn -n -PU xxx.xxx.xxx.xxx/24]for host discovery，The description of -PU in o