Groups > comp.lang.python > #24494 > unrolled thread

PySerial could not open port COM4: [Error 5] Access is denied - please help

Started by	"Adam" <adam@no_thanks.com>
First post	2012-06-26 21:12 -0700
Last post	2012-06-27 14:53 +0000
Articles	20 on this page of 23 — 7 participants

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  PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-26 21:12 -0700
    Re: PySerial could not open port COM4: [Error 5] Access is denied - please help John Nagle <nagle@animats.com> - 2012-06-26 22:33 -0700
      Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 02:10 -0700
        Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Paul <nospam@needed.com> - 2012-06-27 08:28 -0400
          Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 08:26 -0700
            Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Paul <nospam@needed.com> - 2012-06-27 12:04 -0400
              Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 10:41 -0700
                Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Paul <nospam@needed.com> - 2012-06-27 14:04 -0400
                  Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 13:40 -0700
                    Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Grant Edwards <invalid@invalid.invalid> - 2012-06-27 21:18 +0000
                      Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 14:48 -0700
                        Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Grant Edwards <invalid@invalid.invalid> - 2012-06-27 22:06 +0000
                          Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Grant Edwards <invalid@invalid.invalid> - 2012-06-27 22:18 +0000
                            Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Temia Eszteri <lamialily@cleverpun.com> - 2012-06-27 15:31 -0700
                              Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 15:51 -0700
                                Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Grant Edwards <invalid@invalid.invalid> - 2012-06-27 23:24 +0000
                                  Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-27 17:14 -0700
                                    Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Grant Edwards <invalid@invalid.invalid> - 2012-06-28 14:15 +0000
                                      Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "Adam" <adam@no_thanks.com> - 2012-06-28 13:31 -0700
                              Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Roel Schroeven <roel@roelschroeven.net> - 2012-06-28 21:08 +0200
                                Re: PySerial could not open port COM4: [Error 5] Access is denied- please help "Adam" <adam@no_thanks.com> - 2012-06-28 14:48 -0700
        Re: PySerial could not open port COM4: [Error 5] Access is denied - please help "David H. Lipman" <DLipman~nospam~@Verizon.Net> - 2012-06-27 08:28 -0400
          Re: PySerial could not open port COM4: [Error 5] Access is denied - please help Grant Edwards <invalid@invalid.invalid> - 2012-06-27 14:53 +0000

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#24494 — PySerial could not open port COM4: [Error 5] Access is denied - please help

From	"Adam" <adam@no_thanks.com>
Date	2012-06-26 21:12 -0700
Subject	PySerial could not open port COM4: [Error 5] Access is denied - please help
Message-ID	<jse17v$d5n$1@dont-email.me>

Host OS:    Ubuntu 10.04 LTS
Guest OS:    Windows XP Pro SP3


I am able to open port COM4 with Terminal emulator.

So, what can cause PySerial to generate the following error ...

C:\Wattcher>python wattcher.py
Traceback (most recent call last):
  File "wattcher.py", line 56, in <module>
    ser.open()
  File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, in 
open
    raise SerialException("could not open port %s: %s" % (self.portstr, 
ctypes.WinError()))
serial.serialutil.SerialException: could not open port COM4: [Error 5] 
Access is denied.

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#24496

From	John Nagle <nagle@animats.com>
Date	2012-06-26 22:33 -0700
Message-ID	<jse604$1cq$1@dont-email.me>
In reply to	#24494

On 6/26/2012 9:12 PM, Adam wrote:
> Host OS:    Ubuntu 10.04 LTS
> Guest OS:    Windows XP Pro SP3
>
>
> I am able to open port COM4 with Terminal emulator.
>
> So, what can cause PySerial to generate the following error ...
>
> C:\Wattcher>python wattcher.py
> Traceback (most recent call last):
>    File "wattcher.py", line 56, in <module>
>      ser.open()
>    File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, in
> open
>      raise SerialException("could not open port %s: %s" % (self.portstr,
> ctypes.WinError()))
> serial.serialutil.SerialException: could not open port COM4: [Error 5]
> Access is denied.

     Are you trying to access serial ports from a virtual machine?
Which virtual machine environment?  Xen?  VMware? QEmu?  VirtualBox?
I wouldn't expect that to work in most of those.

     What is "COM4", anyway?   Few machines today actually have four
serial ports.  Is some device emulating a serial port?

				John Nagle

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#24498

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 02:10 -0700
Message-ID	<jseim6$tn7$1@dont-email.me>
In reply to	#24496

"John Nagle" <nagle@animats.com> wrote in message 
news:jse604$1cq$1@dont-email.me...
> On 6/26/2012 9:12 PM, Adam wrote:
>> Host OS:    Ubuntu 10.04 LTS
>> Guest OS:    Windows XP Pro SP3
>>
>>
>> I am able to open port COM4 with Terminal emulator.
>>
>> So, what can cause PySerial to generate the following error ...
>>
>> C:\Wattcher>python wattcher.py
>> Traceback (most recent call last):
>>    File "wattcher.py", line 56, in <module>
>>      ser.open()
>>    File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, 
>> in
>> open
>>      raise SerialException("could not open port %s: %s" % (self.portstr,
>> ctypes.WinError()))
>> serial.serialutil.SerialException: could not open port COM4: [Error 5]
>> Access is denied.
>
>     Are you trying to access serial ports from a virtual machine?
> Which virtual machine environment?  Xen?  VMware? QEmu?  VirtualBox?
> I wouldn't expect that to work in most of those.
>
>     What is "COM4", anyway?   Few machines today actually have four
> serial ports.  Is some device emulating a serial port?
>
> John Nagle
>

Thanks, and yes, I am using VirtualBox.  My laptop does not have a serial 
port so
I use a USB-to-serial converter, which is assigned COM4.

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#24506

From	Paul <nospam@needed.com>
Date	2012-06-27 08:28 -0400
Message-ID	<jseu9c$sp3$1@dont-email.me>
In reply to	#24498

Adam wrote:
> "John Nagle" <nagle@animats.com> wrote in message 
> news:jse604$1cq$1@dont-email.me...
>> On 6/26/2012 9:12 PM, Adam wrote:
>>> Host OS:    Ubuntu 10.04 LTS
>>> Guest OS:    Windows XP Pro SP3
>>>
>>>
>>> I am able to open port COM4 with Terminal emulator.
>>>
>>> So, what can cause PySerial to generate the following error ...
>>>
>>> C:\Wattcher>python wattcher.py
>>> Traceback (most recent call last):
>>>    File "wattcher.py", line 56, in <module>
>>>      ser.open()
>>>    File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, 
>>> in
>>> open
>>>      raise SerialException("could not open port %s: %s" % (self.portstr,
>>> ctypes.WinError()))
>>> serial.serialutil.SerialException: could not open port COM4: [Error 5]
>>> Access is denied.
>>     Are you trying to access serial ports from a virtual machine?
>> Which virtual machine environment?  Xen?  VMware? QEmu?  VirtualBox?
>> I wouldn't expect that to work in most of those.
>>
>>     What is "COM4", anyway?   Few machines today actually have four
>> serial ports.  Is some device emulating a serial port?
>>
>> John Nagle
>>
> 
> Thanks, and yes, I am using VirtualBox.  My laptop does not have a serial 
> port so
> I use a USB-to-serial converter, which is assigned COM4.
> 
> 

Doesn't VirtualBox allow "remapping" serial ports ? I thought you
could have COM 4 in the host OS, and make it COM 1 or COM 2 in
the guest. Something like that.

http://virtuatopia.com/images/6/60/Virtualbox_serial_port_settings.jpg

Also, Windows (as a host), is notorious for stealing control of
COM ports. Even Windows software, when you run it, would report
"COM 4 is busy". Then, you have to track down *why* it's busy.
Is it that FAX software you installed ? The GPS software
that talks to your GPS serial interface ?

In theory, the "Handle" program is supposed to identify what
is keeping a COM port busy, but I don't get the desired
results from it very often. You need to know the naming
convention for virtual COM ports (COM4 via USB to serial, is
more virtual than physical). That's what makes it harder
to track down.

These are some names for COM ports, in Windows. The last two entries,
are my USB to serial adapters. VCP1 functions as COM3.
VCP0 functions as COM4. The VCP part is what would be
listed in "Handle" from Sysinternals. The \device\serial
format, is more likely to be used with true "native"
motherboard serial ports.

    \device\serial

    ups.exe pid: 1072 NT AUTHORITY\SYSTEM
       98: File  (---)   \Device\VCP0
    hypertrm.exe pid: 3404 ComputerName\UserID     (claims to use COM3)
       E0: File  (---)   \Device\VCP1

You can download "Handle" and play with it here.

http://technet.microsoft.com/en-us/sysinternals/bb896655

Note that, in my Handle results, at the time I was running
the Windows provided ups.exe to talk to my external UPS
(uninterruptible power supply). So that's what that
reference is. The "hypertrm" one, is me using the
built-in Windows terminal software, to talk to COM3,
to keep the port artificially busy for the purposes
of testing.

If things were working well in your case, you *might*
see something of this form. If not, you'd instead
see the name of the process that has "stolen" the
com port.

    virtualbox.exe pid: 1234 ComputerName\UserID
       E0: File  (---)  \Device\VCP0

HTH,
    Paul

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#24520

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 08:26 -0700
Message-ID	<jsf8nf$13d$1@dont-email.me>
In reply to	#24506

"Paul" <nospam@needed.com> wrote in message 
news:jseu9c$sp3$1@dont-email.me...
> Adam wrote:
>> "John Nagle" <nagle@animats.com> wrote in message 
>> news:jse604$1cq$1@dont-email.me...
>>> On 6/26/2012 9:12 PM, Adam wrote:
>>>> Host OS:    Ubuntu 10.04 LTS
>>>> Guest OS:    Windows XP Pro SP3
>>>>
>>>>
>>>> I am able to open port COM4 with Terminal emulator.
>>>>
>>>> So, what can cause PySerial to generate the following error ...
>>>>
>>>> C:\Wattcher>python wattcher.py
>>>> Traceback (most recent call last):
>>>>    File "wattcher.py", line 56, in <module>
>>>>      ser.open()
>>>>    File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, 
>>>> in
>>>> open
>>>>      raise SerialException("could not open port %s: %s" % 
>>>> (self.portstr,
>>>> ctypes.WinError()))
>>>> serial.serialutil.SerialException: could not open port COM4: [Error 5]
>>>> Access is denied.
>>>     Are you trying to access serial ports from a virtual machine?
>>> Which virtual machine environment?  Xen?  VMware? QEmu?  VirtualBox?
>>> I wouldn't expect that to work in most of those.
>>>
>>>     What is "COM4", anyway?   Few machines today actually have four
>>> serial ports.  Is some device emulating a serial port?
>>>
>>> John Nagle
>>>
>>
>> Thanks, and yes, I am using VirtualBox.  My laptop does not have a serial 
>> port so
>> I use a USB-to-serial converter, which is assigned COM4.
>>
>
> Doesn't VirtualBox allow "remapping" serial ports ? I thought you
> could have COM 4 in the host OS, and make it COM 1 or COM 2 in
> the guest. Something like that.
>
> http://virtuatopia.com/images/6/60/Virtualbox_serial_port_settings.jpg
>
> Also, Windows (as a host), is notorious for stealing control of
> COM ports. Even Windows software, when you run it, would report
> "COM 4 is busy". Then, you have to track down *why* it's busy.
> Is it that FAX software you installed ? The GPS software
> that talks to your GPS serial interface ?
>
> In theory, the "Handle" program is supposed to identify what
> is keeping a COM port busy, but I don't get the desired
> results from it very often. You need to know the naming
> convention for virtual COM ports (COM4 via USB to serial, is
> more virtual than physical). That's what makes it harder
> to track down.
>
> These are some names for COM ports, in Windows. The last two entries,
> are my USB to serial adapters. VCP1 functions as COM3.
> VCP0 functions as COM4. The VCP part is what would be
> listed in "Handle" from Sysinternals. The \device\serial
> format, is more likely to be used with true "native"
> motherboard serial ports.
>
>    \device\serial
>
>    ups.exe pid: 1072 NT AUTHORITY\SYSTEM
>       98: File  (---)   \Device\VCP0
>    hypertrm.exe pid: 3404 ComputerName\UserID     (claims to use COM3)
>       E0: File  (---)   \Device\VCP1
>
> You can download "Handle" and play with it here.
>
> http://technet.microsoft.com/en-us/sysinternals/bb896655
>
> Note that, in my Handle results, at the time I was running
> the Windows provided ups.exe to talk to my external UPS
> (uninterruptible power supply). So that's what that
> reference is. The "hypertrm" one, is me using the
> built-in Windows terminal software, to talk to COM3,
> to keep the port artificially busy for the purposes
> of testing.
>
> If things were working well in your case, you *might*
> see something of this form. If not, you'd instead
> see the name of the process that has "stolen" the
> com port.
>
>    virtualbox.exe pid: 1234 ComputerName\UserID
>       E0: File  (---)  \Device\VCP0
>
> HTH,
>    Paul


Thanks (Guru Paul), I've been using the USB-to-serial converter successfully 
without
enabling/remapping via VBox Settings=>Serial Ports (which are both "not" 
enabled).
I can see the serial port COM4 under Device Manager though.  So, maybe 
enabling is
necessary when the host has "native" serial ports, which my laptop does not 
have.

From the output generated by Handle.exe, here's the section for TeraTerm ...
------------------------------------------------------------------------------
ttermpro.exe pid: 596 VBOX_WINXPPRO\adam        (claims to use COM4)
    C: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313
   2C: Section       \BaseNamedObjects\ttset_memfilemap
   44: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.6028_x-ww_61e65202
   54: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.6195_x-ww_44262b86
   70: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_K32_0_1c9aa25ea688500_7c80_S-1-5-21-1801674531-1078145449-1957994488-1004
   78: File  (RWD)   C:\DOCUME~1\adam\LOCALS~1\Temp\IswTmp\Logs\ISWSHEX.swl
   AC: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_A32_0_1c98aa70f70ec00_77dd_S-1-5-21-1801674531-1078145449-1957994488-1004
  100: Section 
\BaseNamedObjects\CiceroSharedMemDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  108: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313\httplog.log
  120: Section 
\BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004SFM.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  128: Section       \BaseNamedObjects\ShimSharedMemory
  138: Section       \BaseNamedObjects\MSCTF.Shared.SFM.IAB
------------------------------------------------------------------------------

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#24521

From	Paul <nospam@needed.com>
Date	2012-06-27 12:04 -0400
Message-ID	<jsfatv$djt$1@dont-email.me>
In reply to	#24520

Adam wrote:
> "Paul" <nospam@needed.com> wrote in message 
> news:jseu9c$sp3$1@dont-email.me...
>> Adam wrote:
>>> "John Nagle" <nagle@animats.com> wrote in message 
>>> news:jse604$1cq$1@dont-email.me...
>>>> On 6/26/2012 9:12 PM, Adam wrote:
>>>>> Host OS:    Ubuntu 10.04 LTS
>>>>> Guest OS:    Windows XP Pro SP3
>>>>>
>>>>>
>>>>> I am able to open port COM4 with Terminal emulator.
>>>>>
>>>>> So, what can cause PySerial to generate the following error ...
>>>>>
>>>>> C:\Wattcher>python wattcher.py
>>>>> Traceback (most recent call last):
>>>>>    File "wattcher.py", line 56, in <module>
>>>>>      ser.open()
>>>>>    File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, 
>>>>> in
>>>>> open
>>>>>      raise SerialException("could not open port %s: %s" % 
>>>>> (self.portstr,
>>>>> ctypes.WinError()))
>>>>> serial.serialutil.SerialException: could not open port COM4: [Error 5]
>>>>> Access is denied.
>>>>     Are you trying to access serial ports from a virtual machine?
>>>> Which virtual machine environment?  Xen?  VMware? QEmu?  VirtualBox?
>>>> I wouldn't expect that to work in most of those.
>>>>
>>>>     What is "COM4", anyway?   Few machines today actually have four
>>>> serial ports.  Is some device emulating a serial port?
>>>>
>>>> John Nagle
>>>>
>>> Thanks, and yes, I am using VirtualBox.  My laptop does not have a serial 
>>> port so
>>> I use a USB-to-serial converter, which is assigned COM4.
>>>
>> Doesn't VirtualBox allow "remapping" serial ports ? I thought you
>> could have COM 4 in the host OS, and make it COM 1 or COM 2 in
>> the guest. Something like that.
>>
>> http://virtuatopia.com/images/6/60/Virtualbox_serial_port_settings.jpg
>>
>> Also, Windows (as a host), is notorious for stealing control of
>> COM ports. Even Windows software, when you run it, would report
>> "COM 4 is busy". Then, you have to track down *why* it's busy.
>> Is it that FAX software you installed ? The GPS software
>> that talks to your GPS serial interface ?
>>
>> In theory, the "Handle" program is supposed to identify what
>> is keeping a COM port busy, but I don't get the desired
>> results from it very often. You need to know the naming
>> convention for virtual COM ports (COM4 via USB to serial, is
>> more virtual than physical). That's what makes it harder
>> to track down.
>>
>> These are some names for COM ports, in Windows. The last two entries,
>> are my USB to serial adapters. VCP1 functions as COM3.
>> VCP0 functions as COM4. The VCP part is what would be
>> listed in "Handle" from Sysinternals. The \device\serial
>> format, is more likely to be used with true "native"
>> motherboard serial ports.
>>
>>    \device\serial
>>
>>    ups.exe pid: 1072 NT AUTHORITY\SYSTEM
>>       98: File  (---)   \Device\VCP0
>>    hypertrm.exe pid: 3404 ComputerName\UserID     (claims to use COM3)
>>       E0: File  (---)   \Device\VCP1
>>
>> You can download "Handle" and play with it here.
>>
>> http://technet.microsoft.com/en-us/sysinternals/bb896655
>>
>> Note that, in my Handle results, at the time I was running
>> the Windows provided ups.exe to talk to my external UPS
>> (uninterruptible power supply). So that's what that
>> reference is. The "hypertrm" one, is me using the
>> built-in Windows terminal software, to talk to COM3,
>> to keep the port artificially busy for the purposes
>> of testing.
>>
>> If things were working well in your case, you *might*
>> see something of this form. If not, you'd instead
>> see the name of the process that has "stolen" the
>> com port.
>>
>>    virtualbox.exe pid: 1234 ComputerName\UserID
>>       E0: File  (---)  \Device\VCP0
>>
>> HTH,
>>    Paul
> 
> 
> Thanks (Guru Paul), I've been using the USB-to-serial converter successfully 
> without
> enabling/remapping via VBox Settings=>Serial Ports (which are both "not" 
> enabled).
> I can see the serial port COM4 under Device Manager though.  So, maybe 
> enabling is
> necessary when the host has "native" serial ports, which my laptop does not 
> have.
> 
> From the output generated by Handle.exe, here's the section for TeraTerm ...
> ------------------------------------------------------------------------------
> ttermpro.exe pid: 596 VBOX_WINXPPRO\adam        (claims to use COM4)
>     C: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313
>    2C: Section       \BaseNamedObjects\ttset_memfilemap
>    44: File  (RW-) 
> C:\WINDOWS.0\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.6028_x-ww_61e65202
>    54: File  (RW-) 
> C:\WINDOWS.0\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.6195_x-ww_44262b86
>    70: Section 
> \BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_K32_0_1c9aa25ea688500_7c80_S-1-5-21-1801674531-1078145449-1957994488-1004
>    78: File  (RWD)   C:\DOCUME~1\adam\LOCALS~1\Temp\IswTmp\Logs\ISWSHEX.swl
>    AC: Section 
> \BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_A32_0_1c98aa70f70ec00_77dd_S-1-5-21-1801674531-1078145449-1957994488-1004
>   100: Section 
> \BaseNamedObjects\CiceroSharedMemDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
>   108: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313\httplog.log
>   120: Section 
> \BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004SFM.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
>   128: Section       \BaseNamedObjects\ShimSharedMemory
>   138: Section       \BaseNamedObjects\MSCTF.Shared.SFM.IAB
> ------------------------------------------------------------------------------

For Handle to give a positive result, the TeraTerm program would need to
currently have the serial port open. If you haven't started a terminal session,
it might not be listed.

Handle has some kind of filter function, and you can try searching for the name
of the port that way.

I don't see anything in that snipping, which looks like a serial port.

    Paul

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#24524

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 10:41 -0700
Message-ID	<jsfgkr$kf7$1@dont-email.me>
In reply to	#24521

"Paul" <nospam@needed.com> wrote in message 
news:jsfatv$djt$1@dont-email.me...
> Adam wrote:
>> "Paul" <nospam@needed.com> wrote in message 
>> news:jseu9c$sp3$1@dont-email.me...
>>> Adam wrote:
>>>> "John Nagle" <nagle@animats.com> wrote in message 
>>>> news:jse604$1cq$1@dont-email.me...
>>>>> On 6/26/2012 9:12 PM, Adam wrote:
>>>>>> Host OS:    Ubuntu 10.04 LTS
>>>>>> Guest OS:    Windows XP Pro SP3
>>>>>>
>>>>>>
>>>>>> I am able to open port COM4 with Terminal emulator.
>>>>>>
>>>>>> So, what can cause PySerial to generate the following error ...
>>>>>>
>>>>>> C:\Wattcher>python wattcher.py
>>>>>> Traceback (most recent call last):
>>>>>>    File "wattcher.py", line 56, in <module>
>>>>>>      ser.open()
>>>>>>    File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 
>>>>>> 56, in
>>>>>> open
>>>>>>      raise SerialException("could not open port %s: %s" % 
>>>>>> (self.portstr,
>>>>>> ctypes.WinError()))
>>>>>> serial.serialutil.SerialException: could not open port COM4: [Error 
>>>>>> 5]
>>>>>> Access is denied.
>>>>>     Are you trying to access serial ports from a virtual machine?
>>>>> Which virtual machine environment?  Xen?  VMware? QEmu?  VirtualBox?
>>>>> I wouldn't expect that to work in most of those.
>>>>>
>>>>>     What is "COM4", anyway?   Few machines today actually have four
>>>>> serial ports.  Is some device emulating a serial port?
>>>>>
>>>>> John Nagle
>>>>>
>>>> Thanks, and yes, I am using VirtualBox.  My laptop does not have a 
>>>> serial port so
>>>> I use a USB-to-serial converter, which is assigned COM4.
>>>>
>>> Doesn't VirtualBox allow "remapping" serial ports ? I thought you
>>> could have COM 4 in the host OS, and make it COM 1 or COM 2 in
>>> the guest. Something like that.
>>>
>>> http://virtuatopia.com/images/6/60/Virtualbox_serial_port_settings.jpg
>>>
>>> Also, Windows (as a host), is notorious for stealing control of
>>> COM ports. Even Windows software, when you run it, would report
>>> "COM 4 is busy". Then, you have to track down *why* it's busy.
>>> Is it that FAX software you installed ? The GPS software
>>> that talks to your GPS serial interface ?
>>>
>>> In theory, the "Handle" program is supposed to identify what
>>> is keeping a COM port busy, but I don't get the desired
>>> results from it very often. You need to know the naming
>>> convention for virtual COM ports (COM4 via USB to serial, is
>>> more virtual than physical). That's what makes it harder
>>> to track down.
>>>
>>> These are some names for COM ports, in Windows. The last two entries,
>>> are my USB to serial adapters. VCP1 functions as COM3.
>>> VCP0 functions as COM4. The VCP part is what would be
>>> listed in "Handle" from Sysinternals. The \device\serial
>>> format, is more likely to be used with true "native"
>>> motherboard serial ports.
>>>
>>>    \device\serial
>>>
>>>    ups.exe pid: 1072 NT AUTHORITY\SYSTEM
>>>       98: File  (---)   \Device\VCP0
>>>    hypertrm.exe pid: 3404 ComputerName\UserID     (claims to use COM3)
>>>       E0: File  (---)   \Device\VCP1
>>>
>>> You can download "Handle" and play with it here.
>>>
>>> http://technet.microsoft.com/en-us/sysinternals/bb896655
>>>
>>> Note that, in my Handle results, at the time I was running
>>> the Windows provided ups.exe to talk to my external UPS
>>> (uninterruptible power supply). So that's what that
>>> reference is. The "hypertrm" one, is me using the
>>> built-in Windows terminal software, to talk to COM3,
>>> to keep the port artificially busy for the purposes
>>> of testing.
>>>
>>> If things were working well in your case, you *might*
>>> see something of this form. If not, you'd instead
>>> see the name of the process that has "stolen" the
>>> com port.
>>>
>>>    virtualbox.exe pid: 1234 ComputerName\UserID
>>>       E0: File  (---)  \Device\VCP0
>>>
>>> HTH,
>>>    Paul
>>
>>
>> Thanks (Guru Paul), I've been using the USB-to-serial converter 
>> successfully without
>> enabling/remapping via VBox Settings=>Serial Ports (which are both "not" 
>> enabled).
>> I can see the serial port COM4 under Device Manager though.  So, maybe 
>> enabling is
>> necessary when the host has "native" serial ports, which my laptop does 
>> not have.
>>
>> From the output generated by Handle.exe, here's the section for TeraTerm 
>> ...
>> ------------------------------------------------------------------------------
>> ttermpro.exe pid: 596 VBOX_WINXPPRO\adam        (claims to use COM4)
>>     C: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313
>>    2C: Section       \BaseNamedObjects\ttset_memfilemap
>>    44: File  (RW-) 
>> C:\WINDOWS.0\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.6028_x-ww_61e65202
>>    54: File  (RW-) 
>> C:\WINDOWS.0\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.6195_x-ww_44262b86
>>    70: Section 
>> \BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_K32_0_1c9aa25ea688500_7c80_S-1-5-21-1801674531-1078145449-1957994488-1004
>>    78: File  (RWD) 
>> C:\DOCUME~1\adam\LOCALS~1\Temp\IswTmp\Logs\ISWSHEX.swl
>>    AC: Section 
>> \BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_A32_0_1c98aa70f70ec00_77dd_S-1-5-21-1801674531-1078145449-1957994488-1004
>>   100: Section 
>> \BaseNamedObjects\CiceroSharedMemDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
>>   108: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313\httplog.log
>>   120: Section 
>> \BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004SFM.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
>>   128: Section       \BaseNamedObjects\ShimSharedMemory
>>   138: Section       \BaseNamedObjects\MSCTF.Shared.SFM.IAB
>> ------------------------------------------------------------------------------
>
> For Handle to give a positive result, the TeraTerm program would need to
> currently have the serial port open. If you haven't started a terminal 
> session,
> it might not be listed.
>
> Handle has some kind of filter function, and you can try searching for the 
> name
> of the port that way.
>
> I don't see anything in that snipping, which looks like a serial port.
>
>    Paul


Okay, this time I am sure that serial port COM4 is open and
receiving data via telnet.exe (also listed below).

From the output generated by Handle.exe, here's the sections for TeraTerm & 
Telnet ..
------------------------------------------------------------------------------
ttermpro.exe pid: 3808 VBOX_WINXPPRO\adam        (claims to use COM4)
    C: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313
   2C: Section       \BaseNamedObjects\ttset_memfilemap
   44: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.6028_x-ww_61e65202
   54: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.6195_x-ww_44262b86
   70: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_K32_0_1c9aa25ea688500_7c80_S-1-5-21-1801674531-1078145449-1957994488-1004
   78: File  (RWD)   C:\DOCUME~1\adam\LOCALS~1\Temp\IswTmp\Logs\ISWSHEX.swl
   AC: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_A32_0_1c98aa70f70ec00_77dd_S-1-5-21-1801674531-1078145449-1957994488-1004
  100: Section 
\BaseNamedObjects\CiceroSharedMemDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  108: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313\httplog.log
  120: Section 
\BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004SFM.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  128: Section       \BaseNamedObjects\ShimSharedMemory
  138: Section       \BaseNamedObjects\MSCTF.Shared.SFM.IN
  150: Section       \BaseNamedObjects\MSCTF.Shared.SFM.IIM
------------------------------------------------------------------------------
telnet.exe pid: 2408 VBOX_WINXPPRO\adam
   D8: File  (RW-)   D:\Handle
  6EC: Section       \BaseNamedObjects\ShimSharedMemory
  6F4: Section 
\BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004SFM.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  710: Section 
\BaseNamedObjects\CiceroSharedMemDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  740: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_A32_0_1c98aa70f70ec00_77dd_S-1-5-21-1801674531-1078145449-1957994488-1004
  774: File  (RWD)   C:\DOCUME~1\adam\LOCALS~1\Temp\IswTmp\Logs\ISWSHEX.swl
  77C: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_K32_0_1c9aa25ea688500_7c80_S-1-5-21-1801674531-1078145449-1957994488-1004
  798: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.6195_x-ww_44262b86
  79C: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.6028_x-ww_61e65202
------------------------------------------------------------------------------


usage: handle [[-a [-l]] [-u] | [-c <handle> [-y]] | [-s]] [-p 
<process>|<pid>] [name]
  -a      Dump all handle information.
  -l      Just show pagefile-backed section handles.
  -c      Closes the specified handle (interpreted as a hexadecimal number).
          You must specify the process by its PID.
          WARNING: Closing handles can cause application or system 
instability.
  -y      Don't prompt for close handle confirmation.
  -s      Print count of each type of handle open.
  -u      Show the owning user name when searching for handles.
  -p      Dump handles belonging to process (partial name accepted).
  name    Search for handles to objects with <name> (fragment accepted).

No arguments will dump all file references.


Handle type summary:
  Desktop         : 56
  Directory       : 165
  Event           : 3470
  File            : 1463
  IoCompletion    : 142
  Job             : 1
  Key             : 1540
  KeyedEvent      : 49
  Mutant          : 632
  Port            : 566
  Process         : 221
  Section         : 373
  Semaphore       : 1327
  SymbolicLink    : 2
  Thread          : 1009
  Timer           : 46
  Token           : 93
  WaitablePort    : 3
  WindowStation   : 99
  WmiGuid         : 98
Total handles: 11355


This is a tough one.

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#24527

From	Paul <nospam@needed.com>
Date	2012-06-27 14:04 -0400
Message-ID	<jsfhv2$ta9$1@dont-email.me>
In reply to	#24524

Adam wrote:

> 
> 
> This is a tough one.

Try

    handle -a > allhand.txt

Then open the allhand.txt with Notepad and look for interesting entries.

*******

I tested right now, and first opened a session in HyperTerminal with one
of my USB to serial adapters. The second serial adapter, is connect to a
UPS, looking for a shutdown message. So the second entry should be present
at all times.

hypertrm.exe pid: 3452
...
   120: File  (---)   \Device\VCP1

ups.exe pid: 1568 NT AUTHORITY\SYSTEM
...
    98: File  (---)   \Device\VCP0

I don't have any "serial" entries on this machine. But one of
my other machines, has a real COM port on the SuperI/O chip,
so the entries for that would involve the word "serial" in some
way. The USB ones, at least the ones I've got, say VCP. Possibly
because one of the driver files sets up virtual COM ports. There
is a control panel for the driver, that maps a virtual COM port,
to a COM port number, like COM3 and COM4 in this case.

   Paul

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#24538

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 13:40 -0700
Message-ID	<jsfr3i$p6d$1@dont-email.me>
In reply to	#24527

"Paul" <nospam@needed.com> wrote in message 
news:jsfhv2$ta9$1@dont-email.me...
> Adam wrote:
>
>>
>> This is a tough one.
>
> Try
>
>    handle -a > allhand.txt
>
> Then open the allhand.txt with Notepad and look for interesting entries.
>
> *******
>
> I tested right now, and first opened a session in HyperTerminal with one
> of my USB to serial adapters. The second serial adapter, is connect to a
> UPS, looking for a shutdown message. So the second entry should be present
> at all times.
>
> hypertrm.exe pid: 3452
> ...
>   120: File  (---)   \Device\VCP1
>
>
> ups.exe pid: 1568 NT AUTHORITY\SYSTEM
> ...
>    98: File  (---)   \Device\VCP0
>
> I don't have any "serial" entries on this machine. But one of
> my other machines, has a real COM port on the SuperI/O chip,
> so the entries for that would involve the word "serial" in some
> way. The USB ones, at least the ones I've got, say VCP. Possibly
> because one of the driver files sets up virtual COM ports. There
> is a control panel for the driver, that maps a virtual COM port,
> to a COM port number, like COM3 and COM4 in this case.
>
>   Paul


Thanks (Guru Paul), you're the best.  I think we may have something this 
time ...

  144: File  (---)   \Device\ProlificSerial3

And, TeraTerm (using COM4) is open and receiving data wirelessly.

From the output generated by "handle -a", here's the section for TeraTerm 
...
------------------------------------------------------------------------------
ttermpro.exe pid: 3648 VBOX_WINXPPRO\adam        (claims to use COM4)
    4: KeyedEvent    \KernelObjects\CritSecOutOfMemoryEvent
    8: Directory     \KnownDlls
    C: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313
   10: Event
   14: Directory     \Windows
   18: Port
   1C: WindowStation \Windows\WindowStations\WinSta0
   20: Desktop       \Default
   24: WindowStation \Windows\WindowStations\WinSta0
   28: Directory     \BaseNamedObjects
   2C: Section       \BaseNamedObjects\ttset_memfilemap
   30: Semaphore
   34: Semaphore
   38: Key           HKLM
   3C: Event
   40: Semaphore 
\BaseNamedObjects\shell.{A48F1A32-A340-11D1-BC6B-00A0C90312E1}
   44: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.6028_x-ww_61e65202
   48: File  (---)   \Device\KsecDD
   4C: Key           HKCU
   50: Key           HKCU\CLSID
   54: File  (RW-) 
C:\WINDOWS.0\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.6195_x-ww_44262b86
   58: Mutant
   5C: Event         \BaseNamedObjects\crypt32LogoffEvent
   60: Event
   64: Mutant
   68: Event
   6C: Event
   70: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_K32_0_1c9aa25ea688500_7c80_S-1-5-21-1801674531-1078145449-1957994488-1004
   74: Event
   78: File  (RWD)   C:\DOCUME~1\adam\LOCALS~1\Temp\IswTmp\Logs\ISWSHEX.swl
   7C: Semaphore
   80: Semaphore
   84: Semaphore
   88: Semaphore
   8C: Semaphore
   90: Semaphore
   94: Semaphore
   98: Semaphore
   9C: Semaphore
   A0: Semaphore
   A4: Semaphore
   A8: Semaphore
   AC: Section 
\BaseNamedObjects\_ISWINTERNAL_EPT32_SHEX_A32_0_1c98aa70f70ec00_77dd_S-1-5-21-1801674531-1078145449-1957994488-1004
   B0: Port
   B4: Section
   B8: Key           HKCU
   BC: Mutant 
\BaseNamedObjects\CTF.LBES.MutexDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
   C0: File  (---)   \Device\Tcp
   C4: File  (---)   \Device\Tcp
   C8: File  (---)   \Device\Ip
   CC: File  (---)   \Device\Ip
   D0: File  (---)   \Device\Ip
   D4: Semaphore
   D8: Semaphore
   DC: Key           HKLM\SYSTEM\ControlSet001\Services\Tcpip\Linkage
   E0: Key           HKLM\SYSTEM\ControlSet001\Services\Tcpip\Parameters
   E4: Key 
HKLM\SYSTEM\ControlSet001\Services\NetBT\Parameters\Interfaces
   E8: Key           HKLM\SYSTEM\ControlSet001\Services\NetBT\Parameters
   EC: Thread        ttermpro.exe(3648): 3684
   F0: Event
   F4: Key 
HKLM\SYSTEM\ControlSet001\Services\WinSock2\Parameters\Protocol_Catalog9
   F8: Event
   FC: Key 
HKLM\SYSTEM\ControlSet001\Services\WinSock2\Parameters\NameSpace_Catalog5
  100: Section 
\BaseNamedObjects\CiceroSharedMemDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  104: Key           HKLM\SOFTWARE\Microsoft\SystemCertificates\My
  108: File  (RW-)   D:\downloads\Tera Term Pro\ttpro313\httplog.log
  10C: Mutant 
\BaseNamedObjects\CTF.Compart.MutexDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  110: Mutant 
\BaseNamedObjects\CTF.Asm.MutexDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  114: Mutant 
\BaseNamedObjects\CTF.Layouts.MutexDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  118: Mutant 
\BaseNamedObjects\CTF.TMD.MutexDefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  11C: Mutant 
\BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004MUTEX.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  120: Section 
\BaseNamedObjects\CTF.TimListCache.FMPDefaultS-1-5-21-1801674531-1078145449-1957994488-1004SFM.DefaultS-1-5-21-1801674531-1078145449-1957994488-1004
  124: Mutant        \BaseNamedObjects\ShimCacheMutex
  128: Section       \BaseNamedObjects\ShimSharedMemory
  12C: Mutant        \BaseNamedObjects\MSCTF.Shared.MUTEX.IN
  130: Event         \BaseNamedObjects\ReadEnd4
  134: Event
  138: Section       \BaseNamedObjects\MSCTF.Shared.SFM.IN
  13C: Event         \BaseNamedObjects\Write4
  140: Event         \BaseNamedObjects\ReadEnd4
  144: File  (---)   \Device\ProlificSerial3
  148: Event         \BaseNamedObjects\Read4
  14C: Thread        ttermpro.exe(3648): 272
  150: Section       \BaseNamedObjects\MSCTF.Shared.SFM.EGO
  154: Event
  158: Mutant        \BaseNamedObjects\MSCTF.Shared.MUTEX.EGO
------------------------------------------------------------------------------


The Python script needed a call to ser.close() before ser.open() in order to 
work.
Yes, that's right ... things are working fine now.    :-)

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#24543

From	Grant Edwards <invalid@invalid.invalid>
Date	2012-06-27 21:18 +0000
Message-ID	<jsftah$bb5$1@reader1.panix.com>
In reply to	#24538

On 2012-06-27, Adam <adam@no_thanks.com> wrote:

> The Python script needed a call to ser.close() before ser.open() in
> order to work.

IOW, the port opened OK, but when you tried to open it a second time
without closing it first, _that's_ when the .open() call failed.

That's a restriction built in to Win32.  You can't open a serial port
that's already open.  [Linux doesn't have that restriction.]

Why do you need to open it a second time?

-- 
Grant Edwards               grant.b.edwards        Yow! Send your questions to
                                  at               ``ASK ZIPPY'', Box 40474,
                              gmail.com            San Francisco, CA 94140,
                                                   USA

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#24545

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 14:48 -0700
Message-ID	<jsfv3v$imr$1@dont-email.me>
In reply to	#24543

"Grant Edwards" <invalid@invalid.invalid> wrote in message 
news:jsftah$bb5$1@reader1.panix.com...
> On 2012-06-27, Adam <adam@no_thanks.com> wrote:
>
>> The Python script needed a call to ser.close() before ser.open() in
>> order to work.
>
> IOW, the port opened OK, but when you tried to open it a second time
> without closing it first, _that's_ when the .open() call failed.
>
> That's a restriction built in to Win32.  You can't open a serial port
> that's already open.  [Linux doesn't have that restriction.]
>
> Why do you need to open it a second time?
>
> -- 
> Grant Edwards               grant.b.edwards        Yow! Send your 
> questions to
>                                  at               ``ASK ZIPPY'', Box 
> 40474,
>                              gmail.com            San Francisco, CA 94140,
>                                                   USA


As far as I can tell, the wireless hardware connected to the USB-to-serial 
converter is
receiving data (which may have the serial port open?).  I can see the data 
being
received in TeraTerm (using COM4).  After closing TeraTerm,
I start up the Python script and get the following error message ...

C:\Wattcher>python wattcher.py
Traceback (most recent call last):
  File "wattcher.py", line 56, in <module>
    ser.open()
  File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, in
open
    raise SerialException("could not open port %s: %s" % (self.portstr,
ctypes.WinError()))
serial.serialutil.SerialException: could not open port COM4: [Error 5]
Access is denied.


Searching for similar encounters of this error message,
some people said that calling ser.close() before ser.open()
solved the problem.  And, it worked for me as well.

Is this considered a chicken & egg situation?

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#24548

From	Grant Edwards <invalid@invalid.invalid>
Date	2012-06-27 22:06 +0000
Message-ID	<jsg05u$mgk$1@reader1.panix.com>
In reply to	#24545

On 2012-06-27, Adam <adam@no_thanks.com> wrote:
> "Grant Edwards" <invalid@invalid.invalid> wrote:
>> On 2012-06-27, Adam <adam@no_thanks.com> wrote:
>>
>>> The Python script needed a call to ser.close() before ser.open() in
>>> order to work.
>>
>> IOW, the port opened OK, but when you tried to open it a second time
>> without closing it first, _that's_ when the .open() call failed.
>>
>> That's a restriction built in to Win32.  You can't open a serial port
>> that's already open.  [Linux doesn't have that restriction.]
>>
>> Why do you need to open it a second time?
>
> As far as I can tell, the wireless hardware connected to the
> USB-to-serial converter is receiving data (which may have the serial
> port open?).  I can see the data being received in TeraTerm (using
> COM4).  After closing TeraTerm, I start up the Python script and get
> the following error message ...
>
> C:\Wattcher>python wattcher.py
> Traceback (most recent call last):
>   File "wattcher.py", line 56, in <module>
>     ser.open()
>   File "C:\Python25\Lib\site-packages\serial\serialwin32.py", line 56, in
> open
>     raise SerialException("could not open port %s: %s" % (self.portstr,
> ctypes.WinError()))
> serial.serialutil.SerialException: could not open port COM4: [Error 5]
> Access is denied.
>
>
> Searching for similar encounters of this error message, some people
> said that calling ser.close() before ser.open() solved the problem.
> And, it worked for me as well.
>
> Is this considered a chicken & egg situation?

Can you post a small example showing what you're doing?

If you're getting that error (and calling ser.close() makes that error
go away), then it's because you're trying to re-open a port that you
already have open.

What happens if you just get rid of both the ser.close() and
ser.open() calls?  IOW, the port is apparently already open -- why do
you want to close() and then re-open() it?

-- 
Grant Edwards               grant.b.edwards        Yow! I wonder if I should
                                  at               put myself in ESCROW!!
                              gmail.com

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#24551

From	Grant Edwards <invalid@invalid.invalid>
Date	2012-06-27 22:18 +0000
Message-ID	<jsg0sj$4t9$1@reader1.panix.com>
In reply to	#24548

On 2012-06-27, Grant Edwards <invalid@invalid.invalid> wrote:
> On 2012-06-27, Adam <adam@no_thanks.com> wrote:
>> "Grant Edwards" <invalid@invalid.invalid> wrote:

>>> Why do you need to open it a second time?
>>
>> As far as I can tell, the wireless hardware connected to the
>> USB-to-serial converter is receiving data (which may have the serial
>> port open?).  I can see the data being received in TeraTerm (using
>> COM4).  After closing TeraTerm, I start up the Python script and get
>> the following error message ...
[...]
>> Searching for similar encounters of this error message, some people
>> said that calling ser.close() before ser.open() solved the problem.
>> And, it worked for me as well.
>>
>> Is this considered a chicken & egg situation?
>
> Can you post a small example showing what you're doing?

The best way to get help is to write as small a program as possible
that demonstrates the problem, and post it.  I'll help you get
started...

Does this program work?

    import serial
    ser = serial.Serial("COM4")
    ser.close()

At the moment, I don't have access to a Windows machine, but I think
the above should run without any errors.  If it works, then you've
successfully opened and closed the COM4 port.  Start adding
"features", in increments as small as possible, until the program
fails.

Then try to remove stuff that's not needed while still keeping the
failure.

IOW, try to find the smallest possible program that fails.

Usually, in the process of doing that, you'll figure out what you were
doing wrong.  If not, post the smallest failing program you can come
up with, and somebody will be able to help.

If you won't show us what you're doing, we can't tell you what you're
doing wrong.

-- 
Grant Edwards               grant.b.edwards        Yow! Gee, I feel kind of
                                  at               LIGHT in the head now,
                              gmail.com            knowing I can't make my
                                                   satellite dish PAYMENTS!

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#24555

From	Temia Eszteri <lamialily@cleverpun.com>
Date	2012-06-27 15:31 -0700
Message-ID	<ra2nu7h75720i75ijhabg12dngrab756e8@4ax.com>
In reply to	#24551

On Wed, 27 Jun 2012 22:18:59 +0000 (UTC), Grant Edwards
<invalid@invalid.invalid> wrote:

>> Can you post a small example showing what you're doing?
>
>The best way to get help is to write as small a program as possible
>that demonstrates the problem, and post it.  I'll help you get
>started...
>
>Does this program work?
>
>    import serial
>    ser = serial.Serial("COM4")
>    ser.close()
>
>At the moment, I don't have access to a Windows machine, but I think
>the above should run without any errors.  If it works, then you've
>successfully opened and closed the COM4 port.  Start adding
>"features", in increments as small as possible, until the program
>fails.
>
>Then try to remove stuff that's not needed while still keeping the
>failure.
>
>IOW, try to find the smallest possible program that fails.
>
>Usually, in the process of doing that, you'll figure out what you were
>doing wrong.  If not, post the smallest failing program you can come
>up with, and somebody will be able to help.
>
>If you won't show us what you're doing, we can't tell you what you're
>doing wrong.

Actually, I believe someone in an earlier thread in the newsgroup or
elsewhere pointed out that serial ports automatically open under
Windows. I'd have to look it back up when I have the time, which I
don't have at the moment, unfortunately.

~Temia
-- 
The amazing programming device: fuelled entirely by coffee, it codes while
awake and tests while asleep!

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#24557

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 15:51 -0700
Message-ID	<jsg2pt$87s$1@dont-email.me>
In reply to	#24555

"Temia Eszteri" <lamialily@cleverpun.com> wrote in message 
news:ra2nu7h75720i75ijhabg12dngrab756e8@4ax.com...
> On Wed, 27 Jun 2012 22:18:59 +0000 (UTC), Grant Edwards
> <invalid@invalid.invalid> wrote:
>
>>> Can you post a small example showing what you're doing?
>>
>>The best way to get help is to write as small a program as possible
>>that demonstrates the problem, and post it.  I'll help you get
>>started...
>>
>>Does this program work?
>>
>>    import serial
>>    ser = serial.Serial("COM4")
>>    ser.close()
>>
>>At the moment, I don't have access to a Windows machine, but I think
>>the above should run without any errors.  If it works, then you've
>>successfully opened and closed the COM4 port.  Start adding
>>"features", in increments as small as possible, until the program
>>fails.
>>
>>Then try to remove stuff that's not needed while still keeping the
>>failure.
>>
>>IOW, try to find the smallest possible program that fails.
>>
>>Usually, in the process of doing that, you'll figure out what you were
>>doing wrong.  If not, post the smallest failing program you can come
>>up with, and somebody will be able to help.
>>
>>If you won't show us what you're doing, we can't tell you what you're
>>doing wrong.
>
> Actually, I believe someone in an earlier thread in the newsgroup or
> elsewhere pointed out that serial ports automatically open under
> Windows. I'd have to look it back up when I have the time, which I
> don't have at the moment, unfortunately.
>
> ~Temia
> -- 
> The amazing programming device: fuelled entirely by coffee, it codes while
> awake and tests while asleep!


Thanks, I think I read that as well but can't recall where.

I am just running Python scripts (downloaded),
which is not opening the serial port more than once (as Grant keeps 
assuming).

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#24560

From	Grant Edwards <invalid@invalid.invalid>
Date	2012-06-27 23:24 +0000
Message-ID	<jsg4o8$o4p$1@reader1.panix.com>
In reply to	#24557

On 2012-06-27, Adam <adam@no_thanks.com> wrote:
>
>> Actually, I believe someone in an earlier thread in the newsgroup or
>> elsewhere pointed out that serial ports automatically open under
>> Windows. I'd have to look it back up when I have the time, which I
>> don't have at the moment, unfortunately.

What they're referring to is that on startup, Windows used to open
serial ports and query them to see if there was a serial mouse
connected.  If it _thought_ it found a mouse, it would then hold the
port. I don't think that behavior has been enabled by default for a
long time.

If that were the case, then your terminal program wouldn't be able to
open the port either.

However, IIRC, some versions of windows do open and then close the
ports during the bus/device enumeration step of startup. However, they
don't keep the port open, so it doesn't affect the ability of user
applications to later open the port.

> Thanks, I think I read that as well but can't recall where.
>
> I am just running Python scripts (downloaded), which is not opening
> the serial port more than once (as Grant keeps assuming).

Well, I'm assuming your description of what you're doing is accurate.

If you're telling the truth, then the program is opening the port more
than once.

If the port wasn't already open, then calling ser.close() wouldn't do
_anything_.  Here's the close() implmentation from pyserial:

    def close(self):
        """Close port"""
        if self._isOpen:
            if self.hComPort:
                # Restore original timeout values:
                win32.SetCommTimeouts(self.hComPort, self._orgTimeouts)
                # Close COM-Port:
                win32.CloseHandle(self.hComPort)
                win32.CloseHandle(self._overlappedRead.hEvent)
                win32.CloseHandle(self._overlappedWrite.hEvent)
                self.hComPort = None
            self._isOpen = False

There's only _one_ place where self._isOpen is set to True, and that's
at the end of the open() call:

    def open(self):
        """Open port with current settings. This may throw a SerialException
           if the port cannot be opened."""
[...]
        self._overlappedWrite.hEvent = win32.CreateEvent(None, 0, 0, None)
        self._isOpen = True

If you have to add the call "ser.close()" before you can open the port
with "ser.open()", then that means that the port _was_already_open_.

-- 
Grant Edwards               grant.b.edwards        Yow! World War III?
                                  at               No thanks!
                              gmail.com

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#24566

From	"Adam" <adam@no_thanks.com>
Date	2012-06-27 17:14 -0700
Message-ID	<jsg7m0$6mn$1@dont-email.me>
In reply to	#24560

"Grant Edwards" <invalid@invalid.invalid> wrote in message 
news:jsg4o8$o4p$1@reader1.panix.com...
> On 2012-06-27, Adam <adam@no_thanks.com> wrote:
>>
>>> Actually, I believe someone in an earlier thread in the newsgroup or
>>> elsewhere pointed out that serial ports automatically open under
>>> Windows. I'd have to look it back up when I have the time, which I
>>> don't have at the moment, unfortunately.
>
> What they're referring to is that on startup, Windows used to open
> serial ports and query them to see if there was a serial mouse
> connected.  If it _thought_ it found a mouse, it would then hold the
> port. I don't think that behavior has been enabled by default for a
> long time.
>
> If that were the case, then your terminal program wouldn't be able to
> open the port either.
>
> However, IIRC, some versions of windows do open and then close the
> ports during the bus/device enumeration step of startup. However, they
> don't keep the port open, so it doesn't affect the ability of user
> applications to later open the port.
>
>> Thanks, I think I read that as well but can't recall where.
>>
>> I am just running Python scripts (downloaded), which is not opening
>> the serial port more than once (as Grant keeps assuming).
>
> Well, I'm assuming your description of what you're doing is accurate.
>
> If you're telling the truth, then the program is opening the port more
> than once.
>
> If the port wasn't already open, then calling ser.close() wouldn't do
> _anything_.  Here's the close() implmentation from pyserial:
>
>    def close(self):
>        """Close port"""
>        if self._isOpen:
>            if self.hComPort:
>                # Restore original timeout values:
>                win32.SetCommTimeouts(self.hComPort, self._orgTimeouts)
>                # Close COM-Port:
>                win32.CloseHandle(self.hComPort)
>                win32.CloseHandle(self._overlappedRead.hEvent)
>                win32.CloseHandle(self._overlappedWrite.hEvent)
>                self.hComPort = None
>            self._isOpen = False
>
> There's only _one_ place where self._isOpen is set to True, and that's
> at the end of the open() call:
>
>    def open(self):
>        """Open port with current settings. This may throw a 
> SerialException
>           if the port cannot be opened."""
> [...]
>        self._overlappedWrite.hEvent = win32.CreateEvent(None, 0, 0, None)
>        self._isOpen = True
>
> If you have to add the call "ser.close()" before you can open the port
> with "ser.open()", then that means that the port _was_already_open_.
>
> -- 
> Grant Edwards               grant.b.edwards        Yow! World War III?
>                                  at               No thanks!
>                              gmail.com


Obviously pySerial considers the serial port open and will not open an 
already open serial port.
However, why is it that TeraTerm can open the serial port?

Here's the link where I read about calling ser.close() before ser.open() ...

Trying to open a serial port with pyserial on WinXP -> "Access denied"
http://stackoverflow.com/questions/2063257/trying-to-open-a-serial-port-with-pyserial-on-winxp-access-denied


Here's the Python scripts ...
https://github.com/adafruit/Tweet-a-Watt/downloads
Click on the "Download as ..." button for the Python scripts

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#24614

From	Grant Edwards <invalid@invalid.invalid>
Date	2012-06-28 14:15 +0000
Message-ID	<jshotj$s55$1@reader1.panix.com>
In reply to	#24566

On 2012-06-28, Adam <adam@no_thanks.com> wrote:

> Obviously pySerial considers the serial port open

Because it's already been opened by the Python program.

> and will not open an already open serial port.

Pyserial will happily try if you call the open() of a port that's
already open, but Windows will return an error.

> However, why is it that TeraTerm can open the serial port?

Because TeraTerm only opens it once.

> Here's the link where I read about calling ser.close() before
> ser.open() ...
>
> Trying to open a serial port with pyserial on WinXP -> "Access denied"
>
> http://stackoverflow.com/questions/2063257/trying-to-open-a-serial-port-with-pyserial-on-winxp-access-denied

That code is broken.

The port is opened by this line:

 self.ser=serial.Serial(port='\\.\COM1', baudrate=9600, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, timeout=1)

And then the author tries to _open_it_a_second_time_ here:

 self.ser.open()

> Here's the Python scripts ...
> https://github.com/adafruit/Tweet-a-Watt/downloads
> Click on the "Download as ..." button for the Python scripts

Like I kept telling you, those programs are trying to re-open a port
that they've already open.  Here's the erroneous code:

wattcher.py:

    53  
    54  # open up the FTDI serial port to get data transmitted to xbee
    55  ser = serial.Serial(SERIALPORT, BAUDRATE)
    56  ser.open()
    57  

Line 55 opens the serial port.

Line 56 tries to _open_it_again_.  _The_port_is_already_open_. 
Windows doesn't allow a serial port to be opened twice, therefore the
ser.open() call raises an exception.

Just delete line 56.

The same thing happens here:

gmeter-wattcher.py

    83  
    84  # open up the FTDI serial port to get data transmitted to xbee
    85  ser = serial.Serial(SERIALPORT, BAUDRATE)
    86  ser.open()
    87  

Just delete line 86.

See how simple it was to get the problem solved once you posted the
actual code?

-- 
Grant Edwards               grant.b.edwards        Yow! HUMAN REPLICAS are
                                  at               inserted into VATS of
                              gmail.com            NUTRITIONAL YEAST ...

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#24635

From	"Adam" <adam@no_thanks.com>
Date	2012-06-28 13:31 -0700
Message-ID	<jsievj$k72$1@dont-email.me>
In reply to	#24614

"Grant Edwards" <invalid@invalid.invalid> wrote in message 
news:jshotj$s55$1@reader1.panix.com...
> On 2012-06-28, Adam <adam@no_thanks.com> wrote:
>
>> Obviously pySerial considers the serial port open
>
> Because it's already been opened by the Python program.
>
>> and will not open an already open serial port.
>
> Pyserial will happily try if you call the open() of a port that's
> already open, but Windows will return an error.
>
>> However, why is it that TeraTerm can open the serial port?
>
> Because TeraTerm only opens it once.
>
>> Here's the link where I read about calling ser.close() before
>> ser.open() ...
>>
>> Trying to open a serial port with pyserial on WinXP -> "Access denied"
>>
>> http://stackoverflow.com/questions/2063257/trying-to-open-a-serial-port-with-pyserial-on-winxp-access-denied
>
> That code is broken.
>
> The port is opened by this line:
>
> self.ser=serial.Serial(port='\\.\COM1', baudrate=9600, 
> bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, 
> stopbits=serial.STOPBITS_ONE, timeout=1)
>
> And then the author tries to _open_it_a_second_time_ here:
>
> self.ser.open()
>
>> Here's the Python scripts ...
>> https://github.com/adafruit/Tweet-a-Watt/downloads
>> Click on the "Download as ..." button for the Python scripts
>
> Like I kept telling you, those programs are trying to re-open a port
> that they've already open.  Here's the erroneous code:
>
> wattcher.py:
>
>    53
>    54  # open up the FTDI serial port to get data transmitted to xbee
>    55  ser = serial.Serial(SERIALPORT, BAUDRATE)
>    56  ser.open()
>    57
>
> Line 55 opens the serial port.
>
> Line 56 tries to _open_it_again_.  _The_port_is_already_open_.
> Windows doesn't allow a serial port to be opened twice, therefore the
> ser.open() call raises an exception.
>
> Just delete line 56.
>
>
> The same thing happens here:
>
> gmeter-wattcher.py
>
>    83
>    84  # open up the FTDI serial port to get data transmitted to xbee
>    85  ser = serial.Serial(SERIALPORT, BAUDRATE)
>    86  ser.open()
>    87
>
> Just delete line 86.
>
> See how simple it was to get the problem solved once you posted the
> actual code?
>
> -- 
> Grant Edwards               grant.b.edwards        Yow! HUMAN REPLICAS are
>                                  at               inserted into VATS of
>                              gmail.com            NUTRITIONAL YEAST ...


Thanks, Grant !

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#24632

From	Roel Schroeven <roel@roelschroeven.net>
Date	2012-06-28 21:08 +0200
Message-ID	<mailman.1618.1340910525.4697.python-list@python.org>
In reply to	#24555

Temia Eszteri schreef:
> Actually, I believe someone in an earlier thread in the newsgroup or
> elsewhere pointed out that serial ports automatically open under
> Windows. I'd have to look it back up when I have the time, which I
> don't have at the moment, unfortunately.

That doesn't have anything to do with Windows, but with how pySerial 
works. See the documentation for __init__():

"The port is immediately opened on object creation, when a port is 
given. It is not opened when port is None and a successive call to 
open() will be needed."

So if your script does something like

prt = serial.Serial('COM4')

then pySerial automatically opens the port, and you shouldn't call 
prt.open() anymore.

If, on the contrary, you do something like

prt = serial.Serial()
prt.port = 'COM4'

then pySerial doesn't open the port, and you have to call prt.open() to 
do it.

PySerial has this same behavior on both Windows and Linux. The 
difference might be that on Linux it is possible to open serial ports 
more than once, while that doesn't work on Windows.

Best regards,
Roel

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PySerial could not open port COM4: [Error 5] Access is denied - please help

Contents

#24494 — PySerial could not open port COM4: [Error 5] Access is denied - please help

#24496

#24498

#24506

#24520

#24521

#24524

#24527

#24538

#24543

#24545

#24548

#24551

#24555

#24557

#24560

#24566

#24614

#24635

#24632