The "Christensen" file transfer
protocol, probably the most
widely available protocol used for file transfer over
seriallines (e.g. between
modems). XMODEM uses 128-byte
packets
with error detection, allowing the receiver to request
retransmission of a corrupted packet. XModem is fairly slow
but reliable.
Several variations have been proposed with increasing packet
Sending and receiving programs can negotiate to establish the
best protocol they both support.
Standard XMODEM specifies a one-second timeout during the
reception of characters in the data block portion of a packet.
Chuck Forsberg improved upon XMODEM by developing
YMODEM and
[Chuck Forsberg, "XMODEM/YMODEM Protocol Reference"].
(1995-02-02)