What is the XMODEM Protocol?
The XMODEM protocol was developed in 1978 by Ward Christensen. The XMODEM protocol detects errors in transmission through use of either a checksum on old implementations or through a cyclical redundancy check (CRC) in later implementations. XMODEM uses a fixed packet size of 128 bytes and falls into the general category of Half-Duplex ACK/NAK protocols. It must pause after the transmission of every packet until it receives either an ACK or a NAK from the remote system. XMODEM has some significant limitations. For one, XMODEM only works on 8-bit connections. If you must make connections to devices that have 7-bit data paths, XMODEM will not work. Secondly, XMODEM must be run with either no flow control or hardware (RTS/CTS) flow control. If you attempt to run with software (XON/XOFF) flow control, your connection will hang. Thirdly, XMODEM provides no encoding or transparency for control characters. Thus if you attempt to transmit a binary file using XMODEM, the transmission is likely t
