Excel - Monitor - Send/Receive

Python - Monitor

Local Group

Preface

Goal: Monitor excel file changes and show the result in browser using websocket.

This is a multiparts article.

5: Sending and Receiving

Await Asynchronously

Python Source Code

We have to source code here. The sender and the receiver.

Class Skeleton

Sender

The definition is identical with previous code.

class Xl2WebExample:
  def __init__(self, filepath, filename, site, port):
  async def handler(self, websocket, path):
  async def main(self):

Python: Sending and Receiving: Brief

Only the implementation detail of the the handler that are different.

Class: Websocket Handler

Filter

Here we only monitor a particular file, such as /home/epsi/awatchtest-a.xlsx.

  async def handler(self, websocket, path):
    async for changes in awatch(self.filepath):
      xlsx = self.filepath + '/' + self.filename

      for change in changes:
        if change[1] == xlsx:
          print(change[1])
          await websocket.send(change[1])

Python: Sending and Receiving: Handler

The os library is smart enough to differ between slash in linux, or backslash in windows.

      self.xlsx = os.path.join(self.filepath, self.filename)

CLI Client Side

Receiver

This will consumed data sent by the producer.

import asyncio
import websockets

async def push_client():
  async with websockets.\
    connect("ws://localhost:8765") as websocket:
    while True:
      data = await websocket.recv()
      print("Received data:", data)

loop = asyncio.new_event_loop()
loop.run_until_complete(push_client())

All we need to know is the websocket connection.

  async with websockets.\
    connect("ws://localhost:8765") a    self.websocket = websockets websocket:

Output in CLI

Open both, script and python websocket.

Sender in CLI

❯ python 14-send.py

/home/epsi/awatch/test-a.xlsx

Receiver in CLI

❯ python 14-recv.py

Received data: /home/epsi/awatch/test-a.xlsx

Python: Sending and Receiving: Receive

Note that if we close connection from the sender, the receiver will deliver this error messages.

Python: Sending and Receiving: Closed

You can disable the trace back message on Ctrl+c event, by catching the exception handler.

try:
  asyncio.run(example.main())
except KeyboardInterrupt:
  print('Goodbye!')

Web Source Code

Client Side

gitlab.com/…/awatch/site/14-recv.html

We can settle an element to be for value holder.

<body>
    <h1>Your mission. Good Luck!</h1>
    <div id="output"></div>
</body>

And we can retrieve the data using websocket

document.addEventListener(
  "DOMContentLoaded", function(event) {
     const websocket = new WebSocket("ws://localhost:8765");
     const output = document.getElementById("output");

     websocket.onmessage = function(event) {
       const data = event.data; 
       output.innerHTML += `<p>Received: ${data}</p>`;
     }
});