I remember trying out Zmodem early on, only to find that it obviously had some kind of bug in that it would reliably and consistently drop the line after a certain amount of data had been transferred.
Not so, of course - but unlike Xmodem and Ymodem which acknowledged every packet (and slowed things down), Zmodem would not constantly ack back to the host unless there was an error... So this triggered the modem's inactivity timeout, since despite the constant stream of data coming down from the remote system, there were no "keystrokes" or other packets travelling in the other direction. Hence, after X minutes... Line drop.
Easily sorted with a few AT commands, eventually. :)
Not so, of course - but unlike Xmodem and Ymodem which acknowledged every packet (and slowed things down), Zmodem would not constantly ack back to the host unless there was an error... So this triggered the modem's inactivity timeout, since despite the constant stream of data coming down from the remote system, there were no "keystrokes" or other packets travelling in the other direction. Hence, after X minutes... Line drop.
Easily sorted with a few AT commands, eventually. :)