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UDP Hole Punching Timeout

I need to implement UDP protocol. The PC must listen on the dedicated UDP port for incoming packets. It also sends a packet (responses). The application works in Windows XP, 7, 8, ....

Windows Firewall blocks inbound packets. This can be bypassed by UDP holes. So I have to send something that should not hurt. But I want to worry as little as possible.

  • How to determine the timeout before the firewall closes the hole?
  • Can I detect that the firewall has closed the firewall so I have to resend it to open the package? Of course, I won’t get anything when the firewall is closed, but there may be other reasons for this.
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3 answers

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WINHOST=10.116.140.69
mkfifo f
nc -u -p 2222 $WINHOST 6666 < f | \
(while read secs; do for sec in $secs; do echo sleep $sec 1>&2; sleep $sec; echo SLEPT $sec; echo SLEPT $sec 1>&2; done; done) > f

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UNIXHOST=192.168.181.1
nc -u -p 6666 $UNIXHOST 2222

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