CODEWITHSUNDEEP
pythonpyserial
nicolango
nicolango

Reputation: 171

How to know if a port is already open using PySerial?

I'm trying to write an App that uses serial ports in a Linux PC, using python and PySerial. But in this PC there are other Apps using serial ports. How can I know if a port is already open by other App before trying to use it?

Upvotes: 17

Views: 85535

Answers (3)

Fuller
Fuller

Reputation: 83

Check the return output of Serial.serial, it returns an invalid exception that can be caught.

API documentation
Exceptions documentation

Other than that, if the port is in fact closed when your program attempts to access it, the error thrown is non-fatal and is fairly clear about the reason it failed.

Upvotes: 4

Tobias
Tobias

Reputation: 31

This is what me helped when trying to prevent my application from failing because it was stopped and started again.

import serial

try:
  ser = serial.Serial( # set parameters, in fact use your own :-)
    port="COM4",
    baudrate=9600,
    bytesize=serial.SEVENBITS,
    parity=serial.PARITY_EVEN,
    stopbits=serial.STOPBITS_ONE
  )
  ser.isOpen() # try to open port, if possible print message and proceed with 'while True:'
  print ("port is opened!")

except IOError: # if port is already opened, close it and open it again and print message
  ser.close()
  ser.open()
  print ("port was already open, was closed and opened again!")

while True: # do something...

Upvotes: 3

StampyCode
StampyCode

Reputation: 8118

Seems to be badly documented on the PySerial website, this works for me:

ser = serial.Serial(DEVICE,BAUD,timeout=1)
if(ser.isOpen() == False):
    ser.open()

A bit of a contrived example, but you get the idea. I know this question was asked a long time ago, but I had the same question today and felt anyone else finding this page would appreciate finding an answer.

Upvotes: 26

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