如何修复“[错误 6] 句柄无效。”使用 PySerial

Posted 2023-02-23

【中文标题】如何修复“[错误 6] 句柄无效。”使用 PySerial

【英文标题】：How can I fix "[Error 6] The handle is invalid." with PySerial

【发布时间】：2010-06-12 13:15:00

【问题描述】：

我正在尝试使用带有以下代码的 PySerial 从我的 Windows 7 PC 连接到我的手机：

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()

但是在 write 调用时出现以下错误：

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.)

我已尝试使用 TeraTerm 进行连接，效果很好，因此与手机本身的连接没有问题。

我多年来一直在寻找解决方案，但没有找到任何可行的方法。有什么想法吗？

【参考方案1】：

我刚刚在 64 位 Windows（XP、Vista 和 7）上解决了这个问题。

此问题是由于旧的 python-win32 函数导致丢弃 64 位值的高 32 位的无效句柄转换引起的。 如果您遇到此类问题，请使用包含在 win32file 等模块中的新 python-win32 函数。 请在 site-packages\serial\serialwin32.py 上编写以下代码。

#! python
# Python Serial Port Extension for Win32, Linux, BSD, Jython
# serial driver for win32
# see __init__.py
#
# (C) 2001-2009 Chris Liechti <[e-mail]>
# this is distributed under a free software license, see license.txt
#
# Initial patch to use ctypes by Giovanni Bajo <[e-mail]>

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)

【讨论】：

有点像僵尸帖子，但我试过了，现在我遇到了一个新错误，特别是 self.port.flushInput() File "C:\Python27\lib\site- packages\serial\serialwin32.py"，第 273 行，刷新输入 win32.PurgeComm(self.hComPort, win32.PURGE_RXCLEAR | win32.PURGE_RXABORT) ctypes.ArgumentError: argument 1: : wrong type

和@camperdave 一样的问题，有人解决了吗？

我也有类似的烦恼。我认为这个补丁有一个时间和地点已经过去了。尝试 2.6，然后将退回到 2.4。

【参考方案2】：

我在 Windows 7 64 位，使用 python 2.6，它给了我同样的错误。

ser = serial.Serial(3,115200,timeout=1)
ser.read()
#or ser.write("whatever")

Traceback (most recent call last):
  File "<pyshell#3>", line 1, in <module>
    ser.read(1)
  File "build\bdist.win-amd64\egg\serial\serialwin32.py", line 236, in read
    raise SerialException("ReadFile failed (%s)" % ctypes.WinError())
SerialException: ReadFile failed ([Error 6] The handle is invalid.)

当使用使用 c 库的类似程序时，相同的端口会正确响应。这里会发生什么？听起来像是 pyserial 或 ctypes 中的错误。你也用64位吗？

用pyserial写的源码看起来很简单

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
        data = bytes(data)
        if data:
            #~ win32event.ResetEvent(self._overlappedWrite.hEvent)
            n = win32.DWORD()
            err = win32.WriteFile(self.hComPort, data, len(data), ctypes.byref(n), self._overlappedWrite)
            if not err and win32.GetLastError() != win32.ERROR_IO_PENDING:
                raise SerialException("WriteFile failed (%s)" % ctypes.WinError())

64 位 ctype 可能有问题？

---

更新： 至少对我来说绝对是一个 64 位的问题。我刚刚安装了一个 x86 版本的 python（这次是 3.1），现在可以正常工作了。显然 64 位 ctypes 只能导入 64 位库。无法访问操作系统库听起来很奇怪。

【讨论】：

好的，谢谢。正如您所怀疑的，我正在使用 64 位版本的 Python。我会尝试使用 32 位版本。

【参考方案3】：

我观察到 Python 2.7 win7 x64 和 PySerial 2.5 自动从 easy_install.exe 安装的问题

PySerial 2.4 不存在问题，因此如果您的代码与 2.4 兼容，只需使用该代码即可解决问题。请注意，您还必须使用 pywin32，并选择与您的 python 对应的版本（例如 pywin32-216.win-amd64-py2.7.exe）。

另见https://sourceforge.net/tracker/?func=detail&aid=2921959&group_id=46487&atid=446302%5D2921959

【参考方案4】：

这也发生在我身上，实际上是由于我试图访问它时串行端口被关闭。这是因为我使用了一个 'with' 结构，它确保在之后关闭端口，并且错误的代码重构导致了这个问题。

【讨论】：

这最终也是我的问题。谢谢！

【参考方案5】：

使用 pyserial 2.4 版：

http://sourceforge.net/projects/pyserial/files/pyserial/2.4/pyserial-2.4.win32.exe/download