Kermit
A popular packet-oriented protocol from Columbia University for transferring text files and binary files on both full-duplex and half-duplex 8 bit and 7-bit serial connections in a system- and medium-independent fashion, and implemented on hundreds of different computer and operating system platforms. On full-duplex connections a sliding window protocol with selective retransmission provides excellent performance and error recovery characteristics. On 7-bit connections, locking shifts provide efficient transfer of 8-bit data.
When properly implemented, as in the Columbia University Kermit Software collection, performance is equal to or better than other protocols such as ZMODEM, YMODEM, and XMODEM, especially on poor connections.
Kermit is an open protocol - anybody can base their own program on it, but some Kermit software and source code is copyright by Columbia University.