Missing open ports

[Cr4ckC4t]

Problem:
The first version of the code fails to always discover all open ports.

Inspecting the sent and received packets with Wireshark, it appears that although a request for every port is sent, the higher ports miss alot of responses. We get ~68,000 captured packets - 65,535 of which are requests!

Bombarding a machine with requests in such a short timespan (for(i=1; i < 65536; i++) without any delay) floods the target and eventually leads to missing responses from possibly open ports.

Possible fix:
Add an artificial delay between requests to avoid flooding the target.

Experimenting, it turns out that with a delay of 0.00015s we capture around 131,000 packets (out of at least 131.070 expected) at an approximate overall scan time of 30 seconds.

Essentialy, this means portcat could still be missing ~100 ports to check. Important. For a quick port checker it may be acceptable though.

Maybe allow for an easy-to-configure delay variable to tune the port-scanner from fast to reliable.