customers to take action one after the other

Client.py

import asyncio
import json
import random
import websockets
from time import sleep


async def consumer(message):
    if json.loads(message)['next'] == '0':
        sleep(15)  # Do what you want
        return True
    return False


async def consumer_handler(websocket, path):
    async for message in websocket:
        if await consumer(message):
            return


async def producer_handler(websocket, path, message):
    await websocket.send(json.dumps(message))


async def hello(name):
    uri = "ws://localhost:6789"
    async with websockets.connect(uri) as websocket:
        await producer_handler(websocket, '/', {'register': name})
        await consumer_handler(websocket, '/')


name = 'client'
asyncio.get_event_loop().run_until_complete(hello(name))

Server.py

import asyncio
import json
import logging
import websockets

logging.basicConfig()

lock = asyncio.Lock()
USERS = []


def JsonReady():
    return json.dumps({'next' : '0'})

async def NotifyNext():
     if USERS:  # asyncio.wait doesn't accept an empty list
        async with lock:
       
            message = JsonReady()
            v = USERS[0]
            await asyncio.wait([v.send(message)])

            
            
async def NotifyAll():
     if USERS:  # asyncio.wait doesn't accept an empty list
        message = JsonReady()
        await asyncio.wait([user.send(message)for user in USERS])
        
        
async def register(websocket):
    USERS.append(websocket)
    if len(USERS) <= 1:
        await NotifyNext()

async def unregister(websocket):
    USERS.remove(websocket)
    await NotifyNext()



async def Waiter(websocket, path):
    # register(websocket) sends user_event() to websocket
    await register(websocket)
    try:
        async for message in websocket:
            data = json.loads(message)
            print(data['register'])



    finally:
        await unregister(websocket)



start_server = websockets.serve(Waiter, "localhost", 6789)

asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()