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# Serial Backup Server
# Copyright © 2015 Jeffrey Armstrong <jeff@rainbow-100.com>
# http://jeff.rainbow-100.com/
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import time
import serial
import argparse
import os
import os.path
DEFAULT_PORT = 19200
DEFAULT_DEV = '/dev/ttyUSB0'
OK = "OK"
RETRY = "RETRY"
ABORT = "ABORT"
def respond(ser, msg):
"""Writes a response message to the client"""
ser.write(msg)
ser.write(";")
def fletcher16(data):
"""Computes the Fletcher 16 checksum of a data stream"""
c0 = 0
c1 = 0
for b in data:
c0 = (c0 + ord(b))
c1 = (c1 + c0)
cb0 = 255 - ((c0+c1) % 255)
cb1 = 255 - ((c0 + cb0) % 255)
return cb0, cb1
def receive_file(ser, fp):
"""Receives a file block from the client, determines its validity,
and responds accordingly."""
file_contents = b''
length = ord(ser.read())
err = 0
while length > 0:
#print(" receiving {0} bytes".format(length))
bytes = b''
for i in range(0, length):
bytes = bytes + ser.read()
fl1 = ser.read()
fl2 = ser.read()
v1, v2 = fletcher16(bytes)
# print("Fletcher16 - Rainbow({0}, {1}) Python({2}, {3})".format(ord(fl1), ord(fl2), v1, v2))
if (v1 == ord(fl1) and v2 == ord(fl2)):
fp.write(bytes)
respond(ser, OK)
elif err < 10:
respond(ser, RETRY)
err = err + 1
if err == 1:
fp.write(bytes)
print(" block retry {0}...".format(err))
else:
respond(ser, ABORT)
print(" block abort")
break
length = ord(ser.read())
def readtext(ser, bytes=1):
"""Reads a string of bytes from the serial port and converts
them to a string if necessary (i.e. Python 3)"""
b = ser.read(bytes)
try:
return str(b,'ascii')
except TypeError:
return b
def init(ser):
"""Waits for an initialization message from the client"""
print("Waiting for 'ONLINE'...")
while ser.inWaiting() < 6:
time.sleep(1)
x = readtext(ser, 6)
if x == 'ONLINE':
print("Received 'ONLINE' message. Awaiting files...")
return True
return False
def readfilename(ser):
"""Reads the next filename from the client"""
fname = b''
b = ser.read()
while b != b';':
fname = fname + b
b = ser.read()
try:
return str(fname, 'ascii')
except TypeError:
return fname
def prepfile(filename):
"""Returns an open file for writing based on the
reported DOS name"""
newfile = filename.replace(':', '')
if os.sep != '\\':
newfile = newfile.replace('\\', os.sep)
dirs = newfile.split(os.sep)
fullpath = ''
for d in dirs[:-1]:
fullpath = os.path.join(fullpath,d)
if not os.path.exists(fullpath):
os.mkdir(fullpath)
return open(newfile, "w")
def main_transfer(ser):
"""Main program loop"""
# First wait for the online signal
if not init(ser):
print("Initialize failed. Quitting.")
return
while True:
fname = readfilename(ser)
fp = prepfile(fname)
if fp is None:
break
print("Receiving {0}".format(fname))
respond(ser, OK)
receive_file(ser, fp)
fp.close()
def main(port='/dev/ttyUSB0', speed=19200):
"""Opens the serial port and starts the transfer"""
ser = serial.Serial(port, speed)
main_transfer(ser)
ser.close()
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('-p', '--port', dest='port', default='/dev/ttyUSB0')
parser.add_argument('-s', '--speed', dest='speed', type=int, default=19200)
res = parser.parse_args()
main(port=res.port, speed=res.speed)
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