On Thu, 4 Mar 2004, guy keren wrote:
> i am looking for a file-transfer program (for linux), which can run one
> upload and one download simultaneously, on a _single_ TCP connection (sort
> of the TCP equivalent of the BModem protocol used on BBS-es years ago).
>
> i assume this will need to be a client+server application (since standard
> file transfer protocols such as ftp are not 'full-duplex' in this sense).
>
> - it needs to run on the command-line (i.e. NOT an X/svgalib based
> application).
>
> - it needs to show the temporary transfer rate as transfer progresses,
> seperately for each direction (upload/download).
>
> is there such a thing in existence? searching for 'file transfer' +
> 'bidirectional' on freshmeat/google gives nothing. using 'full duplex'
> gives a lot of info about full-duplex ethernet NICS and switches.
>
> by the way, you might ask "what's wrong with using two seperate TCP
> connections - one for upload and one for download?". think of a slow link,
> where a mass download in one direction slows down the ACKs for the upload,
> and vice versa, giving an overall poor performance. (and i don't
> want/can't get into playing with linux's priority queues for this).
How about adjusting TCP send and receive buffers to allow the transmitter
to send several packets before waiting for the first ACK (assuming that
the link does not require too many resends)?
Ref: Tips 7,32 from Jon C. Snader's "Effective TCP/IP Programming"
ISBN 0-201-61589-4, published by Addison-Wesley.
--- Omer
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