Simple multithreaded Server Client Program

Question

I have a multithreaded server and client programs for a simple game. Whenever a client force exits the game, I try to catch the exception with a try catch "except BrokenPipeError" and inform the other players. I also want to end the exited client thread; however, I take input such as this:

while True:
            client = serverSocket.accept()
            t = ServerThread(client)
            t.start()

I tried to use a threading event with stop() function; however, I believe I can not use a .join statement to exit the thread because of the way I take input. How should I end the force exited client. I know that multiprocessing library has a terminate function but I am also required to use the threading library. I tried os_exit(1) but I believe this command kills the entire process. What is the standard exit process for programs such as this?

Answer 1

First of all join() do nothing else but waits for thread to stop. Thread stops when it reaches end of threaded subroutine. For example

class ServerThread(threading.Thread):

   def __init__(self,client,name):
      super().__init__(self)
      self.client = client
      self.name = name

   def inform(self,msg):
      print("{}: got message {}".format( self.name, msg ))
      self.client[0].send(msg)

   def run(self):
      while True:
         try:
            self.client[0].recv(1024)
         except BrokenPipeError: #client exits
            # do stuff
            break # -> ends loop
      return # -> thread exits, join returns

If you want to inform other clients that someone leaves, i would make another monitoring thread

class Monitoring(threading.Thread):

   def __init__(self):
      super().__init__(self,daemon=True) # daemon means thread stops when main thread do
      self.clients=[]

   def add_client(self,client):
      self.clients.append(client)

   def inform_client_leaves(self,client_leaved):
      for client in self.clients:
         if client.is_alive():
            client.inform("Client '{}' leaves".format(client_leaved.name))

   def run(self):
      while True:
         for thread in list(self.threads):
            if not thread.is_alive(): # client exited
               self.threads.remove(thread)
               self.inform_client_exits(thread)
         time.sleep(1)

So the initial code would looks like

mon = Monitoring()
mon.start()
while True:
        client = serverSocket.accept()
        t = ServerThread(client,"Client1")
        t.start()
        mon.add_client(t)