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Editorial Team
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Asked: 2026-05-23T22:31:06+00:00

Say I have an array like this arr = [24, 21, 25, 40, 236,

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Say I have an array like this arr = [24, 21, 25, 40, 236, 89] which is meant to represent an IP address (first four bytes) and a port number (last 2 bytes), as in http://wiki.theory.org/BitTorrentSpecification#Tracker_Response, the binary peer section.

My question is this: how do I get the IP address and the port number from this?

arr[0..3].reverse.join '.' for the IP and arr[5] << 8 | arr[4] for the port doesn’t seem to be correct.

I’m assuming here that since I do string_from_tracker.unpack 'C*' to get arr, the bits are already in the native endianness…

I’m not super sure how this is even supposed to work.

Thanks.

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1 Answer

  1. Editorial Team

    What’s the “not correct part”? I.e. what’s the expected result?

    At least here you have a bug. Combining the two last numbers should be done like so:

    (arr[5] << 8) + arr[4]

    Which gives 23020. Seems more like a Bittorrent port number.

    Edit: Heh 🙂 Actually this is equivalent to the above:

    (arr[5] << 8) | arr[4]
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