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can you recommend a FTP server which

  • supports MODE C (Compression)
  • and runs on Windows or Linux or BSD

Note, that MODE C is different from MODE Z (ZLIB). Most FTP servers on *nix and windows does support mode Z. However I'm aware of only one FTP server which supports MODE C and it runs only IBM Z/OS (successor of OS/390) on IBM Mainframes.

For details on MODE C see http://www.faqs.org/rfcs/rfc959.html section 3.4.3

Martin Vobr
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  • I'm not aware of any Unix/Windows one which does. As well as z/OS, OpenVMS FTP servers commonly do. You can sign up for OpenVMS hobbyist program, install OpenVMS under an emulator, and that way get an FTP server supporting "MODE C". Also, anonymous ftp to ftp.process.com (which runs OpenVMS), then try "quote mode c" then "get readme.txt" - you will see the MODE C block headers in the downloaded file, which your FTP client will think is data because it was expecting a download in MODE S instead. (If you also do "quote stru r", you get a different file - not entirely sure what's going on there.) – Simon Kissane Jun 09 '20 at 19:57

2 Answers2

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I will take the time to answer this question better, although, in essence, Aaron is right. There are no FTP servers on Windows, Linux or UNIX that support MODE C. The z/OS FTP server only supports MODE C for EBCDIC transfer type.

The main reason for this is that MODE C uses run-length encoding for compression which is archaic and not very effective, it is very inefficient with binary data and potentially increases the size of text files.

So, to answer your question, I would recommend against using MODE C!

thecarpy
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  • "MODE B" is needed to transfer record-oriented files (STRU R) while keeping record boundaries. Not significant on platforms without record-oriented file support (Linux/Unix/Windows), but very useful on platforms with that support (z/OS, z/VSE, z/VM, IBM i, OpenVMS, etc). "MODE C" is an extension to "MODE B" designed to compress files with lots of blanks (fixed length records are often padded with blanks or nulls). Never meant to be some kind of general purpose compression scheme and shouldn't be used outside of record-oriented contexts. (Some OpenVMS FTP servers support MODE C but not MODE B.) – Simon Kissane Jun 09 '20 at 20:13
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I checked a whole bunch and I didn't find anything. I think you would have to write one yourself.

Aaron
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