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modem 1.0

Modem implementations for XMODEM, YMODEM and ZMODEM

This package ports the XMODEM, YMODEM and ZMODEM protocols to Python. We try to implement the protocols as minimalistic as possible without breaking the protocol specifications.

The interface to most modem classes are pretty similair. Keep in mind though, that the XMODEM protocol can send one file (stream) at a time, whereas the YMODEM and ZMODEM protocols can send multiple.

All modem implementations must be given a getc callback to retrieve character data from the remote end and a putc callback to send character data.


An example using STDIN/STDOUT may read:

>>> import select
>>> import sys
>>> def getc(size, timeout=5):
...     r, w, e =[sys.stdin.fileno()], [], [], timeout)
...     if r: return
>>> def putc(data, timeout):
...     r, w, e =[], [sys.stdout.fileno()], [], timeout)
...     if w: return sys.stdout.write(data)

Now we can send a stream using XMODEM:

>>> from modem import XMODEM
>>> xmodem = XMODEM(getc, putc)
>>> stream = file(__file__)
>>> xmodem.send(stream)

Or send one or more files using YMODEM or ZMODEM:

>>> from modem import ZMODEM
>>> zmodem = ZMODEM(getc, putc)
>>> zmodem.send([__file__])


About the protocols:

XMODEM:© 1977 Ward Christensen
YMODEM:© 1985 Chunk Forsberg, Omen Technology Inc.
ZMODEM:© 1986 Chunk Forsberg, Omen Technology Inc.

Thanks to:

  • Paolo Perfetti, wrote most of the YMODEM implementation
  • Author: Wijnand Modderman-Lenstra
  • Home Page:
  • Keywords: xmodem ymodem zmodem protocol
  • License: MIT
  • Package Index Owner: tehmaze
  • DOAP record: modem-1.0.xml