1、背景

socket 服务端一直不停的接收客户端连接，当服务端停止时做一些处理操作，比如从数据表中删除某些数据。

如下代码：

import socket


class SocketServer:
    def __init__(self, host, port):
        self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server_address = (host, port)
        self.server_socket.bind(self.server_address)
        self.server_socket.listen(5)

    def handle_client(self, client_socket):
        pass

    def delete_handler(self):
        print("Deleting data")

    def start_server(self):
        try:
            while True:
                client_socket, client_address = self.server_socket.accept()
                self.handle_client(client_socket)
        except KeyboardInterrupt:
            print('Server shutting down.')
        finally:
            self.server_socket.close()
            self.delete_handler()  # 服务端关闭后的处理操作


if __name__ == '__main__':
    server = SocketServer('0.0.0.0', 9999)
    server.start_server()

情况：

1. cmd窗口运行时，按ctrl + c捕捉不到KeyboardInterrupt错误。
2. pycharm运行关闭时也捕捉不到KeyboardInterrupt错误。

2、解决办法1：signal信号机制+threading.Event()（不行）

1. 设置个全局的事件机制
2. 设置信号捕捉ctrl+c
3. 捕捉到后evnet.set()
   • 事件默认false，set()后为True
4. while True 改成while not self.stop_event.is_set()

代码示例：

import socket
import threading
import signal


class SocketServer:
    def __init__(self, host, port):
        self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server_address = (host, port)
        self.server_socket.bind(self.server_address)
        self.server_socket.listen(5)
        self.stop_event = threading.Event()

        # 设置信号处理程序，捕获 Ctrl+C
        signal.signal(signal.SIGINT, self.handle_interrupt)

    def handle_client(self, client_socket):
        pass

    def delete_handler(self):
        print("Deleting data")

    def handle_interrupt(self):
        # 捕获 Ctrl+C 信号，设置停止事件
        self.stop_event.set()

    def start_server(self):
        try:
            while not self.stop_event.is_set():
                client_socket, client_address = self.server_socket.accept()
                self.handle_client(client_socket)
        except KeyboardInterrupt:
            print('Server shutting down.')
        finally:
            self.server_socket.close()
            self.delete_handler()  # 服务端关闭后的处理操作


if __name__ == '__main__':
    server = SocketServer('0.0.0.0', 9999)
    server.start_server()

结果：不行，因为accept已经阻塞住了，一直卡在当前循环，无法进行下一次循环判断。除非接受一条客户段连接，到下次循环之间，恰好按了ctrl+c，这样可以判断到。当然这种实际也是行不通的。

3、解决办法2：单独的线程等待连接（成功）

使用一个单独的线程来等待连接，并在主线程中捕获信号以触发关闭操作。

import socket
import threading
import time


class SocketServer:
    def __init__(self, host, port):
        self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server_address = (host, port)
        self.server_socket.bind(self.server_address)
        self.server_socket.listen(5)
        self.stop_event = threading.Event()

    def handle_client(self, client_socket):
        pass

    def delete_handler(self):
        print("Deleting data")

    def accept_connections(self):
        try:
            while True:
                client_socket, client_address = self.server_socket.accept()
                client_thread = threading.Thread(target=self.handle_client,
                                                 args=(client_socket,))
                client_thread.start()
        except Exception as e:
            print(f'Server error: {e}')

    def start_server(self):
        accept_thread = threading.Thread(target=self.accept_connections, args=())
        accept_thread.start()
        try:
            # 主程序逻辑
            while True:
                time.sleep(1)  # 主线程的其他操作
        except KeyboardInterrupt:
            # 捕获 Ctrl+C
            print('Server shutting down.')
        finally:
            self.server_socket.close()
            self.delete_handler()  # 服务端关闭后的处理操作


if __name__ == '__main__':
    server = SocketServer('0.0.0.0', 9999)
    server.start_server()

实际情况：

1. cmd运行，按ctrl+c后会捕捉到KeyboardInterrupt异常，因此finally里的服务端关闭后的处理操作也会执行。但是命令行还会有输出，应是多线程的问题，还需要点击X号关闭程序。
2. pycharm中运行，关闭时会捕捉到KeyboardInterrupt异常，因此finally里的服务端关闭后的处理操作也会执行。