How can I fix "[Error 6] The handle is invalid." with PySerial
I'm trying to connect to my phone from my Windows 7 PC using PySerial with the following code:
import wmi
import serial
c = wmi.WMI()
modem = c.query("SELECT * FROM Win32_POTSModem").pop()
ser = serial.Serial(modem.AttachedTo, modem.MaxBaudRateToSerialPort)
try:
ser.write('at \r\n')
print ser.readline()
finally:
ser.close()
But get the following error on the write call:
Traceback (most recent call last):
File "D:\Alasdair\Documents\Python Scripts\Phone Interface\test.py", line 14, in <module>
ser.write('at \r\n')
File "C:\Python26\Lib\site-packages\serial\serialwin32.py", line 255, in write
raise SerialException("WriteFile failed (%s)" % ctypes.WinError())
SerialException: WriteFile failed ([Error 6] The handle is invalid.)
I've tried connecting with TeraTerm and that works fine, so it's not a problem with the connection to the phone itself.
I've been searching around for ages trying to find a solution but haven't come up with anything that works. Any ideas?
Answer
I have just fixed this problem on 64bit windows (XP, Vista and 7).
This problem is caused by the invalid handle casting which discard the upper 32-bit of 64-bit value due to old python-win32 functions. If you faced this kind of problem, please use the new python-win32 functions which is included in the win32file etc. modules. Please write the following code over site-packages\serial\serialwin32.py.
#! python
# Python Serial Port Extension for Win32, Linux, BSD, Jython
# serial driver for win32
# see __init__.py
#
# (C) 2001-2009 Chris Liechti <[email protected]>
# this is distributed under a free software license, see license.txt
#
# Initial patch to use ctypes by Giovanni Bajo <[email protected]>
import ctypes
import win32
import win32file
import win32con
import pywintypes
from serialutil import *
def device(portnum):
"""Turn a port number into a device name"""
return 'COM%d' % (portnum+1) # numbers are transformed to a string
class Win32Serial(SerialBase):
"""Serial port implementation for Win32 based on ctypes."""
BAUDRATES = (50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
9600, 19200, 38400, 57600, 115200)
def __init__(self, *args, **kwargs):
self.hComPort = None
SerialBase.__init__(self, *args, **kwargs)
def open(self):
"""Open port with current settings. This may throw a SerialException
if the port cannot be opened."""
if self._port is None:
raise SerialException("Port must be configured before it can be used.")
# the "\\.\COMx" format is required for devices other than COM1-COM8
# not all versions of windows seem to support this properly
# so that the first few ports are used with the DOS device name
port = self.portstr
try:
if port.upper().startswith('COM') and int(port[3:]) > 8:
port = '\\\\.\\' + port
except ValueError:
# for like COMnotanumber
pass
self.hComPort = win32file.CreateFile(port,
win32con.GENERIC_READ | win32con.GENERIC_WRITE,
0, # exclusive access
None, # no security
win32con.OPEN_EXISTING,
win32con.FILE_ATTRIBUTE_NORMAL | win32con.FILE_FLAG_OVERLAPPED,
0)
if self.hComPort == win32.INVALID_HANDLE_VALUE:
self.hComPort = None # 'cause __del__ is called anyway
raise SerialException("could not open port %s: %s" % (self.portstr, ctypes.WinError()))
# Setup a 4k buffer
win32file.SetupComm(self.hComPort, 4096, 4096)
# Save original timeout values:
tos = win32file.GetCommTimeouts(self.hComPort)
self._orgTimeouts = win32.COMMTIMEOUTS(*tos)
self._rtsState = win32.RTS_CONTROL_ENABLE
self._dtrState = win32.DTR_CONTROL_ENABLE
self._reconfigurePort()
# Clear buffers:
# Remove anything that was there
win32file.PurgeComm(self.hComPort,
win32.PURGE_TXCLEAR | win32.PURGE_TXABORT |
win32.PURGE_RXCLEAR | win32.PURGE_RXABORT)
self._overlappedRead = pywintypes.OVERLAPPED()
self._overlappedRead.hEvent = win32.CreateEvent(None, 1, 0, None)
self._overlappedWrite = pywintypes.OVERLAPPED()
#~ self._overlappedWrite.hEvent = win32.CreateEvent(None, 1, 0, None)
self._overlappedWrite.hEvent = win32.CreateEvent(None, 0, 0, None)
self._isOpen = True
def _reconfigurePort(self):
"""Set communication parameters on opened port."""
if not self.hComPort:
raise SerialException("Can only operate on a valid port handle")
# Set Windows timeout values
# timeouts is a tuple with the following items:
# (ReadIntervalTimeout,ReadTotalTimeoutMultiplier,
# ReadTotalTimeoutConstant,WriteTotalTimeoutMultiplier,
# WriteTotalTimeoutConstant)
if self._timeout is None:
timeouts = (0, 0, 0, 0, 0)
elif self._timeout == 0:
timeouts = (win32.MAXDWORD, 0, 0, 0, 0)
else:
timeouts = (0, 0, int(self._timeout*1000), 0, 0)
if self._timeout != 0 and self._interCharTimeout is not None:
timeouts = (int(self._interCharTimeout * 1000),) + timeouts[1:]
if self._writeTimeout is None:
pass
elif self._writeTimeout == 0:
timeouts = timeouts[:-2] + (0, win32.MAXDWORD)
else:
timeouts = timeouts[:-2] + (0, int(self._writeTimeout*1000))
win32file.SetCommTimeouts(self.hComPort, timeouts)
win32file.SetCommMask(self.hComPort, win32.EV_ERR)
# Setup the connection info.
# Get state and modify it:
comDCB = win32file.GetCommState(self.hComPort)
comDCB.BaudRate = self._baudrate
if self._bytesize == FIVEBITS:
comDCB.ByteSize = 5
elif self._bytesize == SIXBITS:
comDCB.ByteSize = 6
elif self._bytesize == SEVENBITS:
comDCB.ByteSize = 7
elif self._bytesize == EIGHTBITS:
comDCB.ByteSize = 8
else:
raise ValueError("Unsupported number of data bits: %r" % self._bytesize)
if self._parity == PARITY_NONE:
comDCB.Parity = win32.NOPARITY
comDCB.fParity = 0 # Disable Parity Check
elif self._parity == PARITY_EVEN:
comDCB.Parity = win32.EVENPARITY
comDCB.fParity = 1 # Enable Parity Check
elif self._parity == PARITY_ODD:
comDCB.Parity = win32.ODDPARITY
comDCB.fParity = 1 # Enable Parity Check
elif self._parity == PARITY_MARK:
comDCB.Parity = win32.MARKPARITY
comDCB.fParity = 1 # Enable Parity Check
elif self._parity == PARITY_SPACE:
comDCB.Parity = win32.SPACEPARITY
comDCB.fParity = 1 # Enable Parity Check
else:
raise ValueError("Unsupported parity mode: %r" % self._parity)
if self._stopbits == STOPBITS_ONE:
comDCB.StopBits = win32.ONESTOPBIT
elif self._stopbits == STOPBITS_ONE_POINT_FIVE:
comDCB.StopBits = win32.ONE5STOPBITS
elif self._stopbits == STOPBITS_TWO:
comDCB.StopBits = win32.TWOSTOPBITS
else:
raise ValueError("Unsupported number of stop bits: %r" % self._stopbits)
comDCB.fBinary = 1 # Enable Binary Transmission
# Char. w/ Parity-Err are replaced with 0xff (if fErrorChar is set to TRUE)
if self._rtscts:
comDCB.fRtsControl = win32.RTS_CONTROL_HANDSHAKE
else:
comDCB.fRtsControl = self._rtsState
if self._dsrdtr:
comDCB.fDtrControl = win32.DTR_CONTROL_HANDSHAKE
else:
comDCB.fDtrControl = self._dtrState
comDCB.fOutxCtsFlow = self._rtscts
comDCB.fOutxDsrFlow = self._dsrdtr
comDCB.fOutX = self._xonxoff
comDCB.fInX = self._xonxoff
comDCB.fNull = 0
comDCB.fErrorChar = 0
comDCB.fAbortOnError = 0
comDCB.XonChar = XON
comDCB.XoffChar = XOFF
win32file.SetCommState(self.hComPort, comDCB)
#~ def __del__(self):
#~ self.close()
def close(self):
"""Close port"""
if self._isOpen:
if self.hComPort:
# Restore original timeout values:
win32file.SetCommTimeouts(self.hComPort, self._orgTimeouts)
# Close COM-Port:
win32file.CloseHandle(self.hComPort)
win32file.CloseHandle(self._overlappedRead.hEvent)
win32file.CloseHandle(self._overlappedWrite.hEvent)
self.hComPort = None
self._isOpen = False
def makeDeviceName(self, port):
return device(port)
# - - - - - - - - - - - - - - - - - - - - - - - -
def inWaiting(self):
"""Return the number of characters currently in the input buffer."""
flags = win32.DWORD()
comstat = win32.COMSTAT()
if not win32file.ClearCommError(self.hComPort, ctypes.byref(flags), ctypes.byref(comstat)):
raise SerialException('call to ClearCommError failed')
return comstat.cbInQue
def read(self, size=1):
"""Read size bytes from the serial port. If a timeout is set it may
return less characters as requested. With no timeout it will block
until the requested number of bytes is read."""
if not self.hComPort: raise portNotOpenError
if size > 0:
win32.ResetEvent(self._overlappedRead.hEvent)
if not win32file.ClearCommError(self.hComPort):
raise SerialException('call to ClearCommError failed')
if self.timeout == 0:
n = min(comstat.cbInQue, size)
if n > 0:
rc,buf = win32file.ReadFile(self.hComPort, n, self._overlappedRead)
if win32.GetLastError() != win32.ERROR_IO_PENDING:
raise SerialException("ReadFile failed (%s)" % ctypes.WinError())
err = win32.WaitForSingleObject(self._overlappedRead.hEvent, win32.INFINITE)
read = buf[:rc]
else:
read = bytes()
else:
rc,buf = win32file.ReadFile(self.hComPort, size, self._overlappedRead)
rc = win32file.GetOverlappedResult(self.hComPort, self._overlappedRead, True)
read = buf[:rc]
else:
read = bytes()
return bytes(read)
def write(self, data):
"""Output the given string over the serial port."""
if not self.hComPort: raise portNotOpenError
#~ if not isinstance(data, (bytes, bytearray)):
#~ raise TypeError('expected %s or bytearray, got %s' % (bytes, type(data)))
# convert data (needed in case of memoryview instance: Py 3.1 io lib), ctypes doesn't like memoryview
if data:
#~ win32event.ResetEvent(self._overlappedWrite.hEvent)
err,n = win32file.WriteFile(self.hComPort, data, self._overlappedWrite)
if not err and win32.GetLastError() != win32.ERROR_IO_PENDING:
raise SerialException("WriteFile failed (%s)" % ctypes.WinError())
# Wait for the write to complete.
#~ win32.WaitForSingleObject(self._overlappedWrite.hEvent, win32.INFINITE)
n = win32file.GetOverlappedResult(self.hComPort, self._overlappedWrite, True)
if n != len(data):
raise writeTimeoutError
return n
else:
return 0
def flushInput(self):
"""Clear input buffer, discarding all that is in the buffer."""
if not self.hComPort: raise portNotOpenError
win32.PurgeComm(self.hComPort, win32.PURGE_RXCLEAR | win32.PURGE_RXABORT)
def flushOutput(self):
"""Clear output buffer, aborting the current output and
discarding all that is in the buffer."""
if not self.hComPort: raise portNotOpenError
win32.PurgeComm(self.hComPort, win32.PURGE_TXCLEAR | win32.PURGE_TXABORT)
def sendBreak(self, duration=0.25):
"""Send break condition. Timed, returns to idle state after given duration."""
if not self.hComPort: raise portNotOpenError
import time
win32.SetCommBreak(self.hComPort)
time.sleep(duration)
win32.ClearCommBreak(self.hComPort)
def setBreak(self, level=1):
"""Set break: Controls TXD. When active, to transmitting is possible."""
if not self.hComPort: raise portNotOpenError
if level:
win32.SetCommBreak(self.hComPort)
else:
win32.ClearCommBreak(self.hComPort)
def setRTS(self, level=1):
"""Set terminal status line: Request To Send"""
if not self.hComPort: raise portNotOpenError
if level:
self._rtsState = win32.RTS_CONTROL_ENABLE
win32.EscapeCommFunction(self.hComPort, win32.SETRTS)
else:
self._rtsState = win32.RTS_CONTROL_DISABLE
win32.EscapeCommFunction(self.hComPort, win32.CLRRTS)
def setDTR(self, level=1):
"""Set terminal status line: Data Terminal Ready"""
if not self.hComPort: raise portNotOpenError
if level:
self._dtrState = win32.DTR_CONTROL_ENABLE
win32.EscapeCommFunction(self.hComPort, win32.SETDTR)
else:
self._dtrState = win32.DTR_CONTROL_DISABLE
win32.EscapeCommFunction(self.hComPort, win32.CLRDTR)
def _GetCommModemStatus(self):
stat = win32.DWORD()
win32.GetCommModemStatus(self.hComPort, ctypes.byref(stat))
return stat.value
def getCTS(self):
"""Read terminal status line: Clear To Send"""
if not self.hComPort: raise portNotOpenError
return win32.MS_CTS_ON & self._GetCommModemStatus() != 0
def getDSR(self):
"""Read terminal status line: Data Set Ready"""
if not self.hComPort: raise portNotOpenError
return win32.MS_DSR_ON & self._GetCommModemStatus() != 0
def getRI(self):
"""Read terminal status line: Ring Indicator"""
if not self.hComPort: raise portNotOpenError
return win32.MS_RING_ON & self._GetCommModemStatus() != 0
def getCD(self):
"""Read terminal status line: Carrier Detect"""
if not self.hComPort: raise portNotOpenError
return win32.MS_RLSD_ON & self._GetCommModemStatus() != 0
# - - platform specific - - - -
def setXON(self, level=True):
"""Platform specific - set flow state."""
if not self.hComPort: raise portNotOpenError
if level:
win32.EscapeCommFunction(self.hComPort, win32.SETXON)
else:
win32.EscapeCommFunction(self.hComPort, win32.SETXOFF)
def outWaiting(self):
"""return how many characters the in the outgoing buffer"""
flags = win32.DWORD()
comstat = win32.COMSTAT()
if not win32.ClearCommError(self.hComPort, ctypes.byref(flags), ctypes.byref(comstat)):
raise SerialException('call to ClearCommError failed')
return comstat.cbOutQue
# assemble Serial class with the platform specific implementation and the base
# for file-like behavior. for Python 2.6 and newer, that provide the new I/O
# library, derive from io.RawIOBase
try:
import io
except ImportError:
# classic version with our own file-like emulation
class Serial(Win32Serial, FileLike):
pass
else:
# io library present
class Serial(Win32Serial, io.RawIOBase):
pass
# Nur Testfunktion!!
if __name__ == '__main__':
s = Serial(0)
sys.stdout.write("%s\n" % s)
s = Serial()
sys.stdout.write("%s\n" % s)
s.baudrate = 19200
s.databits = 7
s.close()
s.port = 0
s.open()
sys.stdout.write("%s\n" % s)