server.py

import socket
import threading

host = '127.0.0.1'
port = 55555

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind((host, port))
server.listen()

clients=[]
nicknames = []

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

def handle(client):
    while True:
        try:
            message=client.recv(1024)
            broadcast(message)
        except:
            index = clients.index(client)
            clients.remove(client)
            client.close()
            nickname = nicknames[index]
            broadcast('{} left!'.format(nickname).encode('ascii'))
            nicknames.remove(nickname)
            break

def reveive():
    while True:
        client,address = server.accept()
        print("Connected with {}".format(str(address)))

        client.send('NICK'.encode('ascii'))
        nickname = client.recv(1024).decode('ascii')
        nicknames.append(nickname)
        clients.append(client)

        print("Nickname is {}".format(nickname))
        broadcast("{} joined!".format(nickname).encode('ascii'))
        client.send('Connected to Server!'.encode('ascii'))
        thread = threading.Thread(target=handle, args=(client,))
        thread.start()

reveive()