isOpen() and is_open always return True

[smurpau]

Same issue here. Fixed delay is the only workaround.

My setup:

• Windows 10
• pyserial 3.4 from pypi
• python 3.6.5
• serial device is a FTDI FT232RL

Tried software flow control, hardware flow control, setting read/write-timeout. In addition I put isOpen() right after serial open and it always returns True, despite silently failing to write (with timeout of 1 second). The read after the write runs into the timeout and does not return the expected repsonse but an empty string.

As a workaround I need to wait for 2 seconds (1 is not enough) and then I can query with the device with read delays of about 30 ms no problem.

If you need to have something tested on my setup, just let me know!

Originally posted by @axel-kah in #329 (comment)

I have the same issue as the above user.

• Windows 10
• pyserial 3.4 from anaconda
• python 3.8.1 x64
• any real or emulated serial device

A call to open() always results in is_open returning True, even if the opening actually failed by timing out. There is thus no way to detect a nonexistent or dropped serial connection, which is quite surprising behaviour to say the least.

The issue appears to arise here: is_open is not set to False on an exception, nor is it set to false in _close(). It is in close(), but that is not called.

[zsquareplusc]

is_open = True is set in the else clause of the try/except, so it will be only true if there is no error. Also at the beginning of the function there is a check that is_openis false. So I do not see how is_open should be in the wrong state.

The example quoted in the issue sounds like a device that is not immediately ready after opening, that's not the fault of the serial port, the OS or this library.