Scapy is a powerful interactive packet manipulation tool, packet
generator, network scanner, network discovery, packet sniffer,
etc. It can for the moment replace hping, 85% of nmap, arpspoof,
arp-sk, arping, tcpdump, tethereal, p0f, ....
In scapy you define a set of packets, then it sends them,
receives answers, matches requests with answers and returns a
list of packet couples (request, answer) and a list of unmatched
packets. This has the big advantage over tools like nmap or
hping that an answer is not reduced to (open/closed/filtered),
but is the whole packet.
I'm the maintainer for the official Debian scapy packages.