I would like to provide a python 3 version of the script to replace native-messaging-example-host. It is tested with Chrome v86 and works as expected. Note that python kernel crashes when tkinter window is closed - this is because of binary data exchange inside threading which causes thread to be hard locked (more info here). I added a command exit to be send from chrome app to stop thread's waiting for another stdin. After receiving it, python won't crash on exit.
Python 3 version (tested with 3.7.4):
# A simple native messaging host. Shows a Tkinter dialog with incoming messages
# that also allows to send message back to the webapp.
import struct
import sys
import threading
import queue as Queue
try:
import tkinter as Tkinter
import tkinter.messagebox
except ImportError:
Tkinter = None
# On Windows, the default I/O mode is O_TEXT. Set this to O_BINARY
# to avoid unwanted modifications of the input/output streams.
if sys.platform == "win32":
import os, msvcrt
msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
# Helper function that sends a message to the webapp.
def send_message(message):
# Write message size.
sys.stdout.buffer.write(struct.pack('I', len(message)))
# Write the message itself.
sys.stdout.write(message)
sys.stdout.flush()
# Thread that reads messages from the webapp.
def read_thread_func(queue):
message_number = 0
while 1:
# Read the message length (first 4 bytes).
text_length_bytes = sys.stdin.buffer.read(4)
if len(text_length_bytes) == 0:
if queue:
queue.put(None)
sys.exit(0)
# Unpack message length as 4 byte integer.
text_length = struct.unpack('@I', text_length_bytes)[0]
# Read the text (JSON object) of the message.
text = sys.stdin.buffer.read(text_length).decode('utf-8')
if text == '{"text":"exit"}':
break
if queue:
queue.put(text)
else:
# In headless mode just send an echo message back.
send_message('{"echo": %s}' % text)
if Tkinter:
class NativeMessagingWindow(tkinter.Frame):
def __init__(self, queue):
self.queue = queue
tkinter.Frame.__init__(self)
self.pack()
self.text = tkinter.Text(self)
self.text.grid(row=0, column=0, padx=10, pady=10, columnspan=2)
self.text.config(state=tkinter.DISABLED, height=10, width=40)
self.messageContent = tkinter.StringVar()
self.sendEntry = tkinter.Entry(self, textvariable=self.messageContent)
self.sendEntry.grid(row=1, column=0, padx=10, pady=10)
self.sendButton = tkinter.Button(self, text="Send", command=self.onSend)
self.sendButton.grid(row=1, column=1, padx=10, pady=10)
self.after(100, self.processMessages)
def processMessages(self):
while not self.queue.empty():
message = self.queue.get_nowait()
if message == None:
self.quit()
return
self.log("Received %s" % message)
self.after(100, self.processMessages)
def onSend(self):
text = '{"text": "' + self.messageContent.get() + '"}'
self.log('Sending %s' % text)
try:
send_message(text)
except IOError:
tkinter.messagebox.showinfo('Native Messaging Example',
'Failed to send message.')
sys.exit(1)
def log(self, message):
self.text.config(state=tkinter.NORMAL)
self.text.insert(tkinter.END, message + "\n")
self.text.config(state=tkinter.DISABLED)
def Main():
if not Tkinter:
send_message('"Tkinter python module wasn\'t found. Running in headless ' +
'mode. Please consider installing Tkinter."')
read_thread_func(None)
sys.exit(0)
queue = Queue.Queue()
main_window = NativeMessagingWindow(queue)
main_window.master.title('Native Messaging Example')
thread = threading.Thread(target=read_thread_func, args=(queue,))
thread.daemon = True
thread.start()
main_window.mainloop()
sys.exit(0)
if __name__ == '__main__':
Main()
Disclaimer: I used 2to3 utility for initial conversion to python 3. I also adopted changes from a webextensions (firefox) version of the nativeMessage API example (it is simplified and not using tkinter gui).
