TCP connection refused using Ngrok in python

Question

I am new to the ngrok and I was trying to create a socket server on python then use ngrok to expose the server over the internet. So far, when I use the url generate from ngrok on my own computer, the connection is successful and I can interact with the server. But when I use computers from other networks, the connection failed. I tried changing the DNS to 8.8.8.8, double checked if the firewall is deactivated etc, but nothing seems to wrong. I sincerely ask anyone who have dealt with similar problems to share their wisdom please. Here is my code:

import threading
import socket
from pyngrok import ngrok
import os

host = "localhost"
port = 3000

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

server_address = ("", port)
server.bind(server_address)
server.listen() # start listening mode

clients = []

# broadcast method
def broadcast(message):
    for client in clients:
        client.send(message)

# Receive messages from client then broadcast
def handle(client, nickname):
    while True:
        try:
            msg = message = client.recv(1024)
            decoded_msg = msg.decode('ascii')
            if msg != '':
                print("{nickname}: {msg}".format(nickname = nickname, msg = decoded_msg))
        except socket.error:
            print("error")

def receive():
    global clients
    while True:
        client, address = server.accept()
        print("Connected by", str(address))

        # ask for nickname
        client.send('Nickname'.encode("ascii"))
        nickname = client.recv(1024).decode('ascii')
        clients.append(client)
        broadcast(f'{nickname} ({address}) joined the Chat\n'.encode('ascii'))
        print(f'{nickname} ({address}) joined the Chat\n')
        client.send('Connected to the Server!\n'.encode('ascii'))

        # Handling Multiple Clients Simultaneously
        thread = threading.Thread(target=handle, args=(client,nickname))
        thread.start()

receive()

and the client code

import socket
import threading
import json
import os

def enter_server():
    os.system("cls||clear") # clear interpreter output
    global nickname
    nickname = input("Choose Your Nickname:")

    host = os.environ.get("HOST")
    port = int(os.environ.get("PORT"))
    global client
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    # Connect to a host
    client.connect((host, port))
    nickname_query = client.recv(1024).decode('ascii')
    print(nickname_query)
    if nickname_query == 'Nickname':
        client.send(nickname.encode('ascii'))
    msg = client.recv(1024).decode('ascii')
    print(msg)

def receive():
    while True:
        try:
            message = client.recv(1024).decode('ascii')
        except socket.error:
            print('Error Occured while Connecting')
            client.close()
            break

def write():
    while True:
        message = input("")
        client.send(message.encode('ascii'))

enter_server()
receive_thread = threading.Thread(target=receive)
receive_thread.start()
write_thread = threading.Thread(target=write)
write_thread.start()

I changed the DNS and took down the firewall, rewrote the code a few times.