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Thread: my cat < /dev/ttySn seems to be interrupted

  1. #1
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    my cat < /dev/ttySn seems to be interrupted

    I sell a home banking (Internet) application. For security reasons it transfers data between computers over an RS232 connection (null modem) with cats at each end. I must not use a network or NFS. It has worked fine at multiple sites for five or so years. At a new site I lose small amounts of data in one place in the file when the transferred file size is large (10K bytes or so). It is as if the cat on the receiving end is interrupted briefly by the operating system, and there is no provision to buffer the incoming data. I do not know how this would be done, only that there has been no problem before. I assume the loss must be at the receiving end. It is not a connection problem because of its consistency.

    The cat is FSF (textutils) version 2.0.14. The UART is on a brand-new Compaq. I hope to learn that someone knows about this.

  2. #2
    Junior Member girlygeek's Avatar
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    I'm not sure about the cat, but I was wondering whether you wouldn't want to consider a point to point network link with a crossover ethernet cable instead.

    That way the TCP/IP stack would be able to handle the buffering, retransmits etc. It would be a more robust solution. The data sent/received on serial ports usually interrupt the main CPU directly, so long streams of of data on a busy processor could give unpredictable results.

  3. #3
    Junior Member girlygeek's Avatar
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    For the TCP solution you could have a non privileged account do the transfers without passwords using private/public crypto keys and then have a cron job running that checks the destination directory periodically for files.

    This soultion would require the installation of a second ethernet NIC though which may not be tolerable for your client.

  4. #4
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    problem with cat

    We understand NFS and TCP/IP and other alternatives. There is a good security reason that one of the computers muust not have any such capabilities; it is stripped. We hope to fix what works for us in many other environments.

    I will replace the hardware and software if I have to, but must travel to do so. It is 500 miles from me.
    Last edited by burkecabaniss; 01-28-2006 at 07:44 PM.

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