Modem hangup problem - Protocols

This is a discussion on Modem hangup problem - Protocols ; Ok, my guess is that this is almost certainly not a Kermit problem, but I thought there might be some people on here that could help. I'm working a a system to receive data via a modem - the model ...

+ Reply to Thread
Results 1 to 4 of 4

Thread: Modem hangup problem

  1. Modem hangup problem

    Ok, my guess is that this is almost certainly not a Kermit problem, but
    I thought there might be some people on here that could help.

    I'm working a a system to receive data via a modem - the model I have
    for it at this point is two external serial port modems. I use kermit
    to dial line 1 from line2, let them handshake and negotiate the
    connection. Then I dump data into the line 2 serial port, and read it
    from the line 1 serial port. Yes, it's crude - but I don't have
    control over the sending end and this appears to be the way the data
    will be sent.

    This works fine for small files. but when I try to send a larger file
    (256K) at some point one or the other modem hangs up or breaks the
    connection at some random point. So far the best I've gotten across is
    ~215K The file that is being sent is a simple binary file - 0 to 255
    repeating.

    I'm guessing this is higher level protocols are for? Can anybody give
    me some insight into what's going on here?
    Thanks
    Eric


  2. Re: Modem hangup problem

    There's no reason Kermit shouldn't work with larger files. I regularly send
    1-5 MB files using Kermit, over both null modem (i.e., hardwired) and dialup
    connections.

    Have you played with maximum packet sizes? I've found that sometimes
    reducing the maximum size makes a borderline connection less likely to
    choke. (SET RECEIVE PACKET n; you might want to try n=90 to start with.)

    --
    Kelvin Smith
    remove "1111" from address for email

    wrote in message
    news:1138662868.847718.244330@f14g2000cwb.googlegr oups.com...
    > Ok, my guess is that this is almost certainly not a Kermit problem, but
    > I thought there might be some people on here that could help.
    >
    > I'm working a a system to receive data via a modem - the model I have
    > for it at this point is two external serial port modems. I use kermit
    > to dial line 1 from line2, let them handshake and negotiate the
    > connection. Then I dump data into the line 2 serial port, and read it
    > from the line 1 serial port. Yes, it's crude - but I don't have
    > control over the sending end and this appears to be the way the data
    > will be sent.
    >
    > This works fine for small files. but when I try to send a larger file
    > (256K) at some point one or the other modem hangs up or breaks the
    > connection at some random point. So far the best I've gotten across is
    > ~215K The file that is being sent is a simple binary file - 0 to 255
    > repeating.
    >
    > I'm guessing this is higher level protocols are for? Can anybody give
    > me some insight into what's going on here?
    > Thanks
    > Eric
    >




  3. Re: Modem hangup problem


    This works fine for small files. but when I try to send a larger file
    (256K) at some point one or the other modem hangs up or breaks the
    connection at some random point. So far the best I've gotten across is
    ~215K The file that is being sent is a simple binary file - 0 to 255
    repeating.

    Send a test file with just standard a-z ascii chars of arbitrarily large
    size.
    You may have a data sequence that is being interpreted as a control signal.




  4. Re: Modem hangup problem

    Kelvin Smith wrote:
    >
    > Have you played with maximum packet sizes? I've found that sometimes
    > reducing the maximum size makes a borderline connection less likely to
    > choke. (SET RECEIVE PACKET n; you might want to try n=90 to start with.)


    My understanding of the OP is that this is a straight text
    send/capture, not a protocol transfer, so things like packet size
    aren't relevant.

    I'm guessing it's some kind of flow control issue. Maybe the receiver
    is choking and tries to stop the data and the sender keeps sending and
    eventually chokes the receiving modem buffer or something like that.
    Possibly reducing the speed of the sender will help if that's going to
    be an option in the real case. Or maybe 'set flow none' on the receiver
    which would result in data loss rather than a lost connection if this
    is the issue. Not a good thing, but it might help pinpoint the problem.

    --
    (for email use this address please - you can figure it out)

    Mark Sapiro msapiro -at- value net Any clod can have the facts;
    San Francisco Bay Area, California having opinions is an art. -
    C. McCabe, The Fearless Spectator


+ Reply to Thread