Simple python script to read two serial ports at the same time. Good for snooping on bidirectional comms!

read_serial.py

#!/usr/bin/python3

import serial, time, sys, threading
from colorama import Fore, Style, init as colorama_init

colorama_init()

# lock to serialize console output
lock = threading.Lock()

class Highlight:
  def __init__(self, clazz, color):
    self.color = color
    self.clazz = clazz
  def __enter__(self):
    print(self.color, end="")
  def __exit__(self, type, value, traceback):
    if self.clazz == Fore:
      print(Fore.RESET, end="")
    else:
      assert self.clazz == Style
      print(Style.RESET_ALL, end="")
    sys.stdout.flush()

if len(sys.argv) != 3 and len(sys.argv) != 4:
  sys.stderr.write("Usage: %s <baud> <port1> [<port2>]\n" % (sys.argv[0]))
  exit(1)

def read_serial(port, baud, color):
  ser = serial.Serial()
  ser.port = port

  ser.baudrate = baud
  ser.bytesize = serial.EIGHTBITS #number of bits per bytes
  ser.parity = serial.PARITY_NONE #set parity check: no parity
  ser.stopbits = serial.STOPBITS_ONE #number of stop bits
  #ser.timeout = None          #block read
  ser.timeout = 0            # non blocking read
  ser.xonxoff = False     #disable software flow control
  ser.rtscts = False     #disable hardware (RTS/CTS) flow control
  ser.dsrdtr = False       #disable hardware (DSR/DTR) flow control
  ser.writeTimeout = 2     #timeout for write

  try:
    ser.open()
  except Exception as e:
    print("error open serial port: " + str(e))
    exit()

  if ser.isOpen():
    try:
        while True:
            c = ser.read(size=1024)
            with lock:
              if len(c) > 0:
                print(color)
                sys.stdout.buffer.write(c)

        ser.close()

    except Exception as e1:
        print ("error communicating...: " + str(e1))

  else:
    print("cannot open serial port ")
    exit()

# Create two threads as follows
try:
   t = threading.Thread(target=read_serial, args=(sys.argv[2], sys.argv[1], Fore.GREEN ))
   t.daemon = True  # thread dies when main thread (only non-daemon thread) exits.
   t.start()

   if len(sys.argv) == 4:
      t = threading.Thread(target=read_serial, args=(sys.argv[3], sys.argv[1], Fore.RED ))
      t.daemon = True  # thread dies when main thread (only non-daemon thread) exits.
      t.start()
except:
   print("Error: unable to start thread")

try:
   while True:
      pass
except KeyboardInterrupt:
   exit()

Muito obrigado, thanks

when I run this code on spyder IDE . i got this error:

runfile('C:/Users/iit/readserial.py', wdir='C:/Users/iit')
Usage: C:/Users/iit/readserial.py []
Error: unable to start thread

line 26 give me error
this line give me error, how to solve thaT?
I want to read COM11, COM15, COM16, COM17 ..

The script is very simple. It is designed to support reading from either one or two serial ports, no more. If you want to read from 4 different ports at the same time, you would need to duplicate these lines (https://gist.github.com/RoganDawes/1042a316a9d320d5e2ff#file-read_serial-py-L74-L77), incrementing the sys.argv argument, and perhaps choosing a different colour.