Tethering is enabled by navigating to the Calculator and entering the following combination without comas: 1642, M+, C, 1452, M+, C, 1943, M+
If the combination was entered correctly the display will read 'run' and tethering will be enabled on HTTP port 6667 and SOCKS port 6668.
Pressing 'C' on the calculator will stop tethering.
You can purchase FlashArmyKnife from the App Store for $1.99.
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