Python client-server using socket.io

What is Socket.io?

Socket.IO is a transport protocol that enables real-time bidirectional event-based communication between clients (typically, though not always, web browsers) and?server.

When a server wants to communicate with a client it?emits?an event.?The client registers event handler functions with the?socketio.Client.event()?or?socketio.Client.on().

Note: It is recommended to create a virtual environment in your working directory for easy installation of required libraries. For details visit?venv — Creation of virtual environments — Python 3.9.7 documentation

Required packages:

pip install python-socketio        

pip install "python-socketio[client]"

pip install eventlet

Server side:

To use socket.io some required libraries are:

socketio

eventlet : This library is used for network-related work. We can use it to run a webserver.

1.?????Creating a server instance.

sio?=?socketio.Server()

2.????We will use Eventlet server.

app?=?socketio.WSGIApp(sio,?static_files={

????'/':?{'content_type':?'text/html',?'filename':?'index.html'}

})

The?wsgi?module provides a simple and easy way to start an event-driven WSGI server. This can serve as an embedded web server in an application.

Eventlet.listen() is a convenience function for opening server sockets.

eventlet.wsgi.server(eventlet.listen(('',?5000)),?app)

3.????On client connection.

@sio.event

def?connect(sid,?environ):

print('server?connected?to?client?with?session?ID?=??',sid)

4.????Upon connection, the server assigns the client a unique session identifier. The application can find this identifier in the?sid?attribute.

print('my sid is', sio.sid)

5.????For sending data to client.

@sio.event

def?my_message(sid,data):

????sio.send(data)

????print('data?sent?from?server?')

6.????For receiving data from client.

@sio.event

def?response(sid,recdata):

????print(recdata)

7.?????Write a disconnect?handler which invokes if application initiated disconnects, server initiated disconnects, or accidental disconnects, for example due to networking failures.

@sio.event

def?disconnect(sid):

????print('disconnect=>SERVER?',?'SID:?',sid)

?

Client side:

1)????Create a client instance.

sio?=?socketio.Client()

2)???Connect to server.

@sio.event

def?connect():

????print('connection?established')

3)???For receiving data from server.

@sio.event

def?message(data):

????print(data)

4)???For sending data to server.

@sio.event

def?send_message():

????sio.emit(event?=?'response',?data?=?{'message':?'HI?from?client'})

????print('data?sent?to?server')

5)???The connection to a server is established by calling the?connect()?method:

sio.connect('https://localhost:5000')

6)???At any time the client can request to be disconnected from the server by invoking the?disconnect()?method:

@sio.event

def?disconnect():

????print('disconnected?from?server=>CLIENT')

7)????If the application does not have anything to do in the main thread and just wants to wait until the connection with the server ends, it can call the?wait()?method:

sio.wait()