select() 调用在调用 setblocking(False) 后仍然阻塞

Question

我有这段服务器端代码：

    def listen_on_port(self):

        try:
            running = True
            HOST = ''                # Symbolic name meaning all available interfaces
            PORT = int(self.port)    # Arbitrary non-privileged port
            server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            server_socket.bind((HOST, PORT))
            server_socket.listen()
            server_socket.setblocking(False)  # non-blocking I/O
            self.logger.info(f'listening on port {self.port}')
            read_list = [server_socket]
            while running:
               try:
                    self.logger.info(f'calling select().')
                    readable, writable, errored = select.select(read_list, [], [])
                    self.logger.info(f'called select().')
                    for s in readable:
                        if s is server_socket:
                            client_socket, address = server_socket.accept()
                            read_list.append(client_socket)
                            self.logger.info(f"Connection from address = {address} client_socket is {client_socket}.")
                        else:
                            self.logger.info(f"going to call s.recv(). s is {s}")
                            try:
                                data = s.recv(1024)
                                self.logger.info(f"Got data = {data}.")
                                if 'terminate' in data.decode('utf-8'):
                                    self.logger.info(f"terminating.")
                                    running = False
                            except Exception as ex:
                                self.logger.info(f'error s.recv() ex={ex}.')
                            finally:
                                self.logger.info(f"closing socket. s = {s}.")
                                s.close()
                                read_list.remove(s)
               except Exception as ex:
                   self.logger.info(f'Inside while True. error ex={ex}.')
                   raise ex
        except Exception as ex:
            self.logger.info(f'error ex={ex}.')

当我运行我的脚本时，我可以在我的日志文件中看到我的代码正在等待 ...

readable, writable, errored = select.select(read_list, [], [])

... 到 return。我的日志文件：

$ cat /tmp/test.log    
doing port 50050
listening on port 50050
calling select().

我打电话给...

server_socket.setblocking(False)  # non-blocking I/O

...但代码仍然阻塞。如果重要的话，我运行正在 mac（不是 Linux 系统）。

Answer 1

select 不关心套接字是否阻塞。如果要进行 non-blocking select 调用，需要指定超时值为 0:

readable, writable, errored = select.select(read_list, [], [], 0)

也就是说，您的代码并没有比阻塞更好的事情。指定 timeout=0 只会将您的 while running 循环变成 busy-wait.

select() 调用在调用 setblocking(False) 后仍然阻塞

select() call still blocking after call to setblocking(False)

python

sockets