hping2 is a network tool able to send custom ICMP/UDP/TCP packets and to display target replies like ping does with ICMP replies. It handles fragmentation and arbitrary packet body and size, and can be used to transfer files under supported protocols. Using hping2, you can test firewall rules, perform (spoofed) port scanning, test network performance using different protocols, do path MTU discovery, perform traceroute-like actions under different protocols, fingerprint remote operating systems, audit TCP/IP stacks, etc.
Yet another great package recommendation from Robert W.:
Good companion to nmap & friends, and shouldn't be missing in your toolbox, especially if you do security work.
More information on this package can be found on the Debian web site.
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