| ''' |
| =============================== |
| XMODEM file transfer protocol |
| =============================== |
| |
| .. $Id$ |
| |
| This is a literal implementation of XMODEM.TXT_, XMODEM1K.TXT_ and |
| XMODMCRC.TXT_, support for YMODEM and ZMODEM is pending. YMODEM should |
| be fairly easy to implement as it is a hack on top of the XMODEM |
| protocol using sequence bytes ``0x00`` for sending file names (and some |
| meta data). |
| |
| .. _XMODEM.TXT: doc/XMODEM.TXT |
| .. _XMODEM1K.TXT: doc/XMODEM1K.TXT |
| .. _XMODMCRC.TXT: doc/XMODMCRC.TXT |
| |
| Data flow example including error recovery |
| ========================================== |
| |
| Here is a sample of the data flow, sending a 3-block message. |
| It includes the two most common line hits - a garbaged block, |
| and an ``ACK`` reply getting garbaged. ``CRC`` or ``CSUM`` represents |
| the checksum bytes. |
| |
| XMODEM 128 byte blocks |
| ---------------------- |
| |
| :: |
| |
| SENDER RECEIVER |
| |
| <-- NAK |
| SOH 01 FE Data[128] CSUM --> |
| <-- ACK |
| SOH 02 FD Data[128] CSUM --> |
| <-- ACK |
| SOH 03 FC Data[128] CSUM --> |
| <-- ACK |
| SOH 04 FB Data[128] CSUM --> |
| <-- ACK |
| SOH 05 FA Data[100] CPMEOF[28] CSUM --> |
| <-- ACK |
| EOT --> |
| <-- ACK |
| |
| XMODEM-1k blocks, CRC mode |
| -------------------------- |
| |
| :: |
| |
| SENDER RECEIVER |
| |
| <-- C |
| STX 01 FE Data[1024] CRC CRC --> |
| <-- ACK |
| STX 02 FD Data[1024] CRC CRC --> |
| <-- ACK |
| STX 03 FC Data[1000] CPMEOF[24] CRC CRC --> |
| <-- ACK |
| EOT --> |
| <-- ACK |
| |
| Mixed 1024 and 128 byte Blocks |
| ------------------------------ |
| |
| :: |
| |
| SENDER RECEIVER |
| |
| <-- C |
| STX 01 FE Data[1024] CRC CRC --> |
| <-- ACK |
| STX 02 FD Data[1024] CRC CRC --> |
| <-- ACK |
| SOH 03 FC Data[128] CRC CRC --> |
| <-- ACK |
| SOH 04 FB Data[100] CPMEOF[28] CRC CRC --> |
| <-- ACK |
| EOT --> |
| <-- ACK |
| |
| YMODEM Batch Transmission Session (1 file) |
| ------------------------------------------ |
| |
| :: |
| |
| SENDER RECEIVER |
| <-- C (command:rb) |
| SOH 00 FF foo.c NUL[123] CRC CRC --> |
| <-- ACK |
| <-- C |
| SOH 01 FE Data[128] CRC CRC --> |
| <-- ACK |
| SOH 02 FC Data[128] CRC CRC --> |
| <-- ACK |
| SOH 03 FB Data[100] CPMEOF[28] CRC CRC --> |
| <-- ACK |
| EOT --> |
| <-- NAK |
| EOT --> |
| <-- ACK |
| <-- C |
| SOH 00 FF NUL[128] CRC CRC --> |
| <-- ACK |
| |
| |
| ''' |
| |
| __author__ = 'Wijnand Modderman <maze@pyth0n.org>' |
| __copyright__ = ['Copyright (c) 2010 Wijnand Modderman', |
| 'Copyright (c) 1981 Chuck Forsberg'] |
| __license__ = 'MIT' |
| __version__ = '0.3.2' |
| |
| import logging |
| import time |
| import sys |
| from functools import partial |
| import collections |
| |
| # Loggerr |
| log = logging.getLogger('xmodem') |
| |
| # Protocol bytes |
| SOH = bytes([0x01]) |
| STX = bytes([0x02]) |
| EOT = bytes([0x04]) |
| ACK = bytes([0x06]) |
| DLE = bytes([0x10]) |
| NAK = bytes([0x15]) |
| CAN = bytes([0x18]) |
| CRC = bytes([0x43]) # C |
| |
| |
| class XMODEM(object): |
| ''' |
| XMODEM Protocol handler, expects an object to read from and an object to |
| write to. |
| |
| >>> def getc(size, timeout=1): |
| ... return data or None |
| ... |
| >>> def putc(data, timeout=1): |
| ... return size or None |
| ... |
| >>> modem = XMODEM(getc, putc) |
| |
| |
| :param getc: Function to retrieve bytes from a stream |
| :type getc: callable |
| :param putc: Function to transmit bytes to a stream |
| :type putc: callable |
| :param mode: XMODEM protocol mode |
| :type mode: string |
| :param pad: Padding character to make the packets match the packet size |
| :type pad: char |
| |
| ''' |
| |
| # crctab calculated by Mark G. Mendel, Network Systems Corporation |
| crctable = [ |
| 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, |
| 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, |
| 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, |
| 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, |
| 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, |
| 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, |
| 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, |
| 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, |
| 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, |
| 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, |
| 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, |
| 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, |
| 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, |
| 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, |
| 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, |
| 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, |
| 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, |
| 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, |
| 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, |
| 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, |
| 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, |
| 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, |
| 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, |
| 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, |
| 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, |
| 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, |
| 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, |
| 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, |
| 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, |
| 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, |
| 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, |
| 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0, |
| ] |
| |
| def __init__(self, getc, putc, mode='xmodem', pad=b'\x1a'): |
| self.getc = getc |
| self.putc = putc |
| self.mode = mode |
| self.pad = pad |
| |
| def abort(self, count=2, timeout=60): |
| ''' |
| Send an abort sequence using CAN bytes. |
| ''' |
| for counter in range(0, count): |
| self.putc(CAN, timeout) |
| |
| def send(self, stream, retry=32, timeout=360, quiet=0, callback=None): |
| ''' |
| Send a stream via the XMODEM protocol. |
| |
| >>> stream = file('/etc/issue', 'rb') |
| >>> print modem.send(stream) |
| True |
| |
| Returns ``True`` upon successful transmission or ``False`` in case of |
| failure. |
| |
| :param stream: The stream object to send data from. |
| :type stream: stream (file, etc.) |
| :param retry: The maximum number of times to try to resend a failed |
| packet before failing. |
| :type retry: int |
| :param timeout: The number of seconds to wait for a response before |
| timing out. |
| :type timeout: int |
| :param quiet: If 0, it prints info to stderr. If 1, it does not print any info. |
| :type quiet: int |
| :param callback: Reference to a callback function that has the |
| following signature. This is useful for |
| getting status updates while a xmodem |
| transfer is underway. |
| Expected callback signature: |
| def callback(total_packets, success_count, error_count) |
| :type callback: callable |
| ''' |
| |
| # initialize protocol |
| try: |
| packet_size = dict( |
| xmodem = 128, |
| xmodem1k = 1024, |
| )[self.mode] |
| except AttributeError: |
| raise ValueError("An invalid mode was supplied") |
| |
| error_count = 0 |
| crc_mode = 0 |
| cancel = 0 |
| while True: |
| char = self.getc(1) |
| if char: |
| if char == NAK: |
| crc_mode = 0 |
| break |
| elif char == CRC: |
| crc_mode = 1 |
| break |
| elif char == CAN: |
| if not quiet: |
| print('received CAN', file=sys.stderr) |
| if cancel: |
| return False |
| else: |
| cancel = 1 |
| else: |
| log.error('send ERROR expected NAK/CRC, got %s' % \ |
| (ord(char),)) |
| |
| error_count += 1 |
| if error_count >= retry: |
| self.abort(timeout=timeout) |
| return False |
| |
| # send data |
| error_count = 0 |
| success_count = 0 |
| total_packets = 0 |
| sequence = 1 |
| while True: |
| data = stream.read(packet_size) |
| if not data: |
| log.info('sending EOT') |
| # end of stream |
| break |
| total_packets += 1 |
| data = data.ljust(packet_size, self.pad) |
| if crc_mode: |
| crc = self.calc_crc(data) |
| else: |
| crc = self.calc_checksum(data) |
| |
| # emit packet |
| while True: |
| if packet_size == 128: |
| self.putc(SOH) |
| else: # packet_size == 1024 |
| self.putc(STX) |
| self.putc(bytes([sequence])) |
| self.putc(bytes([0xff - sequence])) |
| self.putc(data) |
| if crc_mode: |
| self.putc(bytes([crc >> 8])) |
| self.putc(bytes([crc & 0xff])) |
| else: |
| self.putc(bytes([crc])) |
| |
| char = self.getc(1, timeout) |
| if char == ACK: |
| success_count += 1 |
| if isinstance(callback, collections.Callable): |
| callback(total_packets, success_count, error_count) |
| break |
| if char == NAK: |
| error_count += 1 |
| if isinstance(callback, collections.Callable): |
| callback(total_packets, success_count, error_count) |
| if error_count >= retry: |
| # excessive amounts of retransmissions requested, |
| # abort transfer |
| self.abort(timeout=timeout) |
| log.warning('excessive NAKs, transfer aborted') |
| return False |
| |
| # return to loop and resend |
| continue |
| else: |
| log.error('Not ACK, Not NAK') |
| error_count += 1 |
| if isinstance(callback, collections.Callable): |
| callback(total_packets, success_count, error_count) |
| if error_count >= retry: |
| # excessive amounts of retransmissions requested, |
| # abort transfer |
| self.abort(timeout=timeout) |
| log.warning('excessive protocol errors, transfer aborted') |
| return False |
| |
| # return to loop and resend |
| continue |
| |
| # protocol error |
| self.abort(timeout=timeout) |
| log.error('protocol error') |
| return False |
| |
| # keep track of sequence |
| sequence = (sequence + 1) % 0x100 |
| |
| while True: |
| # end of transmission |
| self.putc(EOT) |
| |
| #An ACK should be returned |
| char = self.getc(1, timeout) |
| if char == ACK: |
| break |
| else: |
| error_count += 1 |
| if error_count >= retry: |
| self.abort(timeout=timeout) |
| log.warning('EOT was not ACKd, transfer aborted') |
| return False |
| |
| return True |
| |
| def recv(self, stream, crc_mode=1, retry=16, timeout=60, delay=1, quiet=0): |
| ''' |
| Receive a stream via the XMODEM protocol. |
| |
| >>> stream = file('/etc/issue', 'wb') |
| >>> print modem.recv(stream) |
| 2342 |
| |
| Returns the number of bytes received on success or ``None`` in case of |
| failure. |
| ''' |
| |
| # initiate protocol |
| error_count = 0 |
| char = 0 |
| cancel = 0 |
| while True: |
| # first try CRC mode, if this fails, |
| # fall back to checksum mode |
| if error_count >= retry: |
| self.abort(timeout=timeout) |
| return None |
| elif crc_mode and error_count < (retry / 2): |
| if not self.putc(CRC): |
| time.sleep(delay) |
| error_count += 1 |
| else: |
| crc_mode = 0 |
| if not self.putc(NAK): |
| time.sleep(delay) |
| error_count += 1 |
| |
| char = self.getc(1, timeout) |
| if not char: |
| error_count += 1 |
| continue |
| elif char == SOH: |
| #crc_mode = 0 |
| break |
| elif char == STX: |
| break |
| elif char == CAN: |
| if cancel: |
| return None |
| else: |
| cancel = 1 |
| else: |
| error_count += 1 |
| |
| # read data |
| error_count = 0 |
| income_size = 0 |
| packet_size = 128 |
| sequence = 1 |
| cancel = 0 |
| while True: |
| while True: |
| if char == SOH: |
| packet_size = 128 |
| break |
| elif char == STX: |
| packet_size = 1024 |
| break |
| elif char == EOT: |
| # We received an EOT, so send an ACK and return the received |
| # data length |
| self.putc(ACK) |
| return income_size |
| elif char == CAN: |
| # cancel at two consecutive cancels |
| if cancel: |
| return None |
| else: |
| cancel = 1 |
| else: |
| if not quiet: |
| print('recv ERROR expected SOH/EOT, got', ord(char), file=sys.stderr) |
| error_count += 1 |
| if error_count >= retry: |
| self.abort() |
| return None |
| # read sequence |
| error_count = 0 |
| cancel = 0 |
| seq1 = ord(self.getc(1)) |
| seq2 = 0xff - ord(self.getc(1)) |
| if seq1 == sequence and seq2 == sequence: |
| # sequence is ok, read packet |
| # packet_size + checksum |
| data = self.getc(packet_size + 1 + crc_mode, timeout) |
| if crc_mode: |
| csum = (ord(data[-2]) << 8) + ord(data[-1]) |
| data = data[:-2] |
| log.debug('CRC (%04x <> %04x)' % \ |
| (csum, self.calc_crc(data))) |
| valid = csum == self.calc_crc(data) |
| else: |
| csum = data[-1] |
| data = data[:-1] |
| log.debug('checksum (checksum(%02x <> %02x)' % \ |
| (ord(csum), self.calc_checksum(data))) |
| valid = ord(csum) == self.calc_checksum(data) |
| |
| # valid data, append chunk |
| if valid: |
| income_size += len(data) |
| stream.write(data) |
| self.putc(ACK) |
| sequence = (sequence + 1) % 0x100 |
| char = self.getc(1, timeout) |
| continue |
| else: |
| # consume data |
| self.getc(packet_size + 1 + crc_mode) |
| self.debug('expecting sequence %d, got %d/%d' % \ |
| (sequence, seq1, seq2)) |
| |
| # something went wrong, request retransmission |
| self.putc(NAK) |
| |
| def calc_checksum(self, data, checksum=0): |
| ''' |
| Calculate the checksum for a given block of data, can also be used to |
| update a checksum. |
| |
| >>> csum = modem.calc_checksum('hello') |
| >>> csum = modem.calc_checksum('world', csum) |
| >>> hex(csum) |
| '0x3c' |
| |
| ''' |
| return (sum(map(ord, data)) + checksum) % 256 |
| |
| def calc_crc(self, data, crc=0): |
| ''' |
| Calculate the Cyclic Redundancy Check for a given block of data, can |
| also be used to update a CRC. |
| |
| >>> crc = modem.calc_crc('hello') |
| >>> crc = modem.calc_crc('world', crc) |
| >>> hex(crc) |
| '0xd5e3' |
| |
| ''' |
| for char in data: |
| crc = (crc << 8) ^ self.crctable[((crc >> 8) ^ int(char)) & 0xff] |
| return crc & 0xffff |
| |
| |
| XMODEM1k = partial(XMODEM, mode='xmodem1k') |
| |
| |
| def run(): |
| import optparse |
| import subprocess |
| |
| parser = optparse.OptionParser(usage='%prog [<options>] <send|recv> filename filename') |
| parser.add_option('-m', '--mode', default='xmodem', |
| help='XMODEM mode (xmodem, xmodem1k)') |
| |
| options, args = parser.parse_args() |
| if len(args) != 3: |
| parser.error('invalid arguments') |
| return 1 |
| |
| elif args[0] not in ('send', 'recv'): |
| parser.error('invalid mode') |
| return 1 |
| |
| def _func(so, si): |
| import select |
| import subprocess |
| |
| print('si', si) |
| print('so', so) |
| |
| def getc(size, timeout=3): |
| w,t,f = select.select([so], [], [], timeout) |
| if w: |
| data = so.read(size) |
| else: |
| data = None |
| |
| print('getc(', repr(data), ')') |
| return data |
| |
| def putc(data, timeout=3): |
| w,t,f = select.select([], [si], [], timeout) |
| if t: |
| si.write(data) |
| si.flush() |
| size = len(data) |
| else: |
| size = None |
| |
| print('putc(', repr(data), repr(size), ')') |
| return size |
| |
| return getc, putc |
| |
| def _pipe(*command): |
| pipe = subprocess.Popen(command, |
| stdout=subprocess.PIPE, stdin=subprocess.PIPE) |
| return pipe.stdout, pipe.stdin |
| |
| if args[0] == 'recv': |
| import io |
| getc, putc = _func(*_pipe('sz', '--xmodem', args[2])) |
| stream = open(args[1], 'wb') |
| xmodem = XMODEM(getc, putc, mode=options.mode) |
| status = xmodem.recv(stream, retry=8) |
| stream.close() |
| |
| elif args[0] == 'send': |
| getc, putc = _func(*_pipe('rz', '--xmodem', args[2])) |
| stream = open(args[1], 'rb') |
| xmodem = XMODEM(getc, putc, mode=options.mode) |
| status = xmodem.send(stream, retry=8) |
| stream.close() |
| |
| if __name__ == '__main__': |
| sys.exit(run()) |
