Thread missing 1 required positional argument

Question

Just to give some context: I'm currently learning Python and to do so I started a little Project.

I wrote two Python Scripts: a Host and a Client script.

I'm already at the point where multiple Clients can connect to one "Host" and the Host can send a random String to all Clients.

Now I wanted to solve the problem, that if a Client disconnects from the Host nobody knows until the CLIENTSOCKET is called again.

So I wrote the checkConnection method to ping all Clients every 5 sec, for now.

class Connection():

    def __init__(self):
        self.s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

    def bound(self,RHOST,PORT):
        self.s.bind((RHOST,PORT))
        self.s.listen(1000)

    def connect(self):
        ((CLIENTSOCKET,ADRESS)) = self.s.accept()
        return (CLIENTSOCKET,ADRESS)

def newConnection(Connection,CLIENTS):
    con = Connection
    cli = CLIENTS
    while True:
        c = con.connect()
        if c != None:
            if len(cli) != 0:
                for x in range (len(cli)):

                    if c[1][0] == cli[x][1][0]:
                        pass
                    else:
                        cli.append(c)
            else:
                cli.append(c)

def checkConnection(CLIENTS):
    cli = CLIENTS
    while True:
        if(len(cli)!=0):
            for x in range(len(cli)):
                try:
                    cli[x][0].sendall(b'')
                except:
                    del cli[x]
            time.sleep(5)

I'm creating to Threads with each method as a target and give them the needed parameters. The first thread starts like it should, but the second doesn't.

I really don't know why?

t = threading.Thread(target = newConnection,name = "newConnection",args = (g,CLIENTS))
t2 = threading.Thread(target = checkConnection,name = "checkConnection",args = (CLIENTS))
t.start()
t2.start()

Exception in thread checkConnection:

Traceback (most recent call last):
  File "C:\Users\User\AppData\Local\Programs\Python\Python35-32\lib\threading.py", line 914, in _bootstrap_inner
    self.run()
  File "C:\Users\User\AppData\Local\Programs\Python\Python35-32\lib\threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
TypeError: checkConnection() missing 1 required positional argument: 'CLIENTS'