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Comment by bombcar | Hacker News Reader

Aren't there some other ones? IIRC the standard "IP address handler library" would do things like "try any possible way of interpreting it" and would work on words, etc.

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There are no officially adopted text-representations (for IPv4), only binary ones. In other words: there are simultaneously infinitely more possibilities and exactly zero.

For the most part, applications tend to punt the job of interpreting such text address representations to the IP stack (usually embedded in the OS kernel). These vary in what they'll accept by implementation and version, but they tend to be extremely good at interpreting whatever arbitrary nonsense people have historically been likely to try. As a result, there are surprisingly few application-level libraries which even attempt to deal with that mess.

I only know of two operating systems where IP address parsing (and the address resolver in general) is part of the TCP/IP stack: ITS and z/OS. MS-DOS gets an honorable mention due to not having any architectural distinction between parts of the system at all, and z/OS only qualifies because it's not entirely clear where the boundaries of the "TCP/IP stack" are to begin with. (One would be forgiven for thinking that the TCP/IP stack is contained in the address space called "TCPIP". However, significant parts of it are in the LPA, which is part of every address space, and it's not clear to me yet where exactly the resolver is.)

You could represent each octet as an ASCII char reducing it to 4 characters.

Or 5 base85 digits if you wanted to ensure there were no control characters...

> You could represent each octet as an ASCII char reducing it to 4 characters.

Except ASCII is 7-bit, and a number of those are control characters. So you couldn’t, and many that you could would be unreadable. <DEL><NUL><NUL><SOH> for localhost is... not ideal.

That sounds like good laptop sticker material. Could even give readers a hint by using the "there's no place like" saying that I've seen applied to 127.0.0.1 and ::1 already, or prefix some hacking tool. I wonder how many people would get it.

There's no place like <DEL><NUL><NUL><SOH>

You can type control codes (except for NUL, DEL, CR, LF?) on the Linux console by pressing Ctrl+letter. Might add some security to your disk encryption password, unless you need to enter it from a GUI :)

How do you write DEL, which Ctrl+key is that? I had written this actually as ^H^@^@^A, but realized that ^H may remove characters but is not DEL, so I edited that out of my previous comment.

Yes, I don't know if there is any key combination to type DEL. Ctrl just clears bit 6. ^S and ^Q are also problematic because of XON/XOFF. I did use ^G (BEEP!) in a password once.

edit ^H is also swallowed by the line editor of course.

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