Python网络与多任务编程:TCP/UDP实战指南
一、网络编程
1.1 前言
网络编程是现代软件开发中不可或缺的一部分,它使得不同设备之间的数据交换成为可能。Python提供了强大的标准库来支持各种网络编程需求。
1.1.1 IP地址简介
IP地址是互联网上设备的唯一标识符,分为IPv4和IPv6两种格式:
import socket# 获取本机IP地址
hostname = socket.gethostname()
ip_address = socket.gethostbyname(hostname)
print(f"主机名: {hostname}")
print(f"IP地址: {ip_address}")# 域名解析
domain = "www.google.com"
try:ip = socket.gethostbyname(domain)print(f"{domain} 的IP地址是: {ip}")
except socket.gaierror:print(f"无法解析域名: {domain}")
1.1.2 端口和端口号简介
端口是网络通信的端点,端口号范围是0-65535,其中0-1023为知名端口,一般由系统服务使用。
# 常见端口号示例
common_ports = {"HTTP": 80,"HTTPS": 443,"FTP": 21,"SSH": 22,"SMTP": 25,"DNS": 53
}print("常见服务端口号:")
for service, port in common_ports.items():print(f"{service}: {port}")
1.1.3 字符串数据编解码
网络传输中数据需要以字节形式传输,因此需要进行编解码操作:
# 字符串编码与解码
text = "你好,世界!"# 编码为字节
encoded_data = text.encode('utf-8')
print(f"编码后: {encoded_data}")# 解码为字符串
decoded_text = encoded_data.decode('utf-8')
print(f"解码后: {decoded_text}")# 其他编码方式
text_gbk = text.encode('gbk')
print(f"GBK编码: {text_gbk}")
1.2 TCP
1.2.1 TCP介绍
TCP(传输控制协议)是一种面向连接的、可靠的、基于字节流的传输层通信协议。它提供全双工通信,确保数据顺序传输且不丢失。
1.2.2 TCP客户端开发
1.2.2.1 发送数据
import socketdef tcp_client_send(host='127.0.0.1', port=8888):"""TCP客户端发送数据"""# 创建TCP socketclient_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)try:# 连接服务器client_socket.connect((host, port))print(f"已连接到服务器 {host}:{port}")# 发送数据message = "Hello, TCP Server!"client_socket.send(message.encode('utf-8'))print(f"已发送: {message}")except Exception as e:print(f"连接错误: {e}")finally:# 关闭连接client_socket.close()print("连接已关闭")if __name__ == "__main__":tcp_client_send()
1.2.2.2 发送并接收数据
def tcp_client_send_receive(host='127.0.0.1', port=8888):"""TCP客户端发送并接收数据"""client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)try:client_socket.connect((host, port))print(f"已连接到服务器 {host}:{port}")# 发送数据message = "Hello, Server! How are you?"client_socket.send(message.encode('utf-8'))print(f"已发送: {message}")# 接收响应response = client_socket.recv(1024).decode('utf-8')print(f"收到响应: {response}")except Exception as e:print(f"错误: {e}")finally:client_socket.close()print("连接已关闭")if __name__ == "__main__":tcp_client_send_receive()
1.2.3 TCP服务器开发
1.2.3.1 接收客户端消息并回复
def tcp_server_simple(host='127.0.0.1', port=8888):"""简单的TCP服务器,接收消息并回复"""# 创建TCP socketserver_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)# 设置地址重用server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)# 绑定地址和端口server_socket.bind((host, port))# 开始监听,设置最大连接数server_socket.listen(5)print(f"服务器启动,监听 {host}:{port}")try:while True:# 接受客户端连接client_socket, client_address = server_socket.accept()print(f"接收到来自 {client_address} 的连接")try:# 接收客户端数据data = client_socket.recv(1024).decode('utf-8')if data:print(f"收到消息: {data}")# 回复客户端response = f"服务器已收到你的消息: {data}"client_socket.send(response.encode('utf-8'))except Exception as e:print(f"处理客户端数据时出错: {e}")finally:# 关闭客户端连接client_socket.close()print(f"与 {client_address} 的连接已关闭")except KeyboardInterrupt:print("服务器被用户中断")finally:# 关闭服务器socketserver_socket.close()print("服务器已关闭")if __name__ == "__main__":tcp_server_simple()
1.2.3.2 接收客户端的多条信息
def tcp_server_multiple_messages(host='127.0.0.1', port=8888):"""处理客户端多条消息的TCP服务器"""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(5)print(f"服务器启动,监听 {host}:{port}")try:while True:client_socket, client_address = server_socket.accept()print(f"接收到来自 {client_address} 的连接")try:# 持续接收客户端消息while True:data = client_socket.recv(1024).decode('utf-8')if not data:print(f"{client_address} 断开连接")breakprint(f"收到来自 {client_address} 的消息: {data}")# 处理特殊命令if data.lower() == 'exit':response = "再见!"client_socket.send(response.encode('utf-8'))breakelif data.lower() == 'time':from datetime import datetimeresponse = f"当前时间: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}"client_socket.send(response.encode('utf-8'))else:response = f"已收到: {data}"client_socket.send(response.encode('utf-8'))except ConnectionResetError:print(f"{client_address} 异常断开连接")except Exception as e:print(f"处理 {client_address} 时出错: {e}")finally:client_socket.close()except KeyboardInterrupt:print("服务器被用户中断")finally:server_socket.close()print("服务器已关闭")if __name__ == "__main__":tcp_server_multiple_messages()
1.2.3.3 允许客户端多次连接
import threadingdef handle_client(client_socket, client_address):"""处理客户端连接的线程函数"""print(f"开始处理 {client_address} 的连接")try:while True:data = client_socket.recv(1024).decode('utf-8')if not data:print(f"{client_address} 断开连接")breakprint(f"收到来自 {client_address} 的消息: {data}")# 回复客户端response = f"服务器已收到: {data}"client_socket.send(response.encode('utf-8'))except ConnectionResetError:print(f"{client_address} 异常断开连接")except Exception as e:print(f"处理 {client_address} 时出错: {e}")finally:client_socket.close()print(f"{client_address} 的连接已关闭")def tcp_server_multiple_clients(host='127.0.0.1', port=8888):"""支持多客户端连接的TCP服务器"""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(5)print(f"服务器启动,监听 {host}:{port}")try:while True:client_socket, client_address = server_socket.accept()print(f"接收到来自 {client_address} 的连接")# 为每个客户端创建新线程client_thread = threading.Thread(target=handle_client, args=(client_socket, client_address))client_thread.daemon = Trueclient_thread.start()except KeyboardInterrupt:print("服务器被用户中断")finally:server_socket.close()print("服务器已关闭")if __name__ == "__main__":tcp_server_multiple_clients()
1.2.4 TCP开发总结
- TCP特点:面向连接、可靠传输、流量控制、拥塞控制
- 适用场景:需要可靠数据传输的应用,如文件传输、邮件、Web浏览
- 开发要点:
- 客户端使用connect()连接服务器
- 服务器使用bind()绑定地址,listen()监听,accept()接受连接
- 使用send()和recv()进行数据传输
- 及时关闭连接释放资源
- 处理异常和连接中断情况
1.3 UDP
1.3.1 UDP介绍
UDP(用户数据报协议)是一种无连接的传输层协议,提供不可靠的数据报服务。它不保证数据顺序和可靠性,但传输效率高。
1.3.2 UDP发送端开发
def udp_sender(host='127.0.0.1', port=9999):"""UDP发送端"""# 创建UDP socketudp_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)try:while True:# 获取用户输入message = input("请输入要发送的消息 (输入 'exit' 退出): ")if message.lower() == 'exit':break# 发送数据udp_socket.sendto(message.encode('utf-8'), (host, port))print(f"已发送到 {host}:{port}: {message}")except Exception as e:print(f"发送错误: {e}")finally:udp_socket.close()print("UDP发送端已关闭")if __name__ == "__main__":udp_sender()
1.3.3 UDP接收端开发
def udp_receiver(host='127.0.0.1', port=9999):"""UDP接收端"""# 创建UDP socketudp_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)# 绑定地址和端口udp_socket.bind((host, port))print(f"UDP接收端启动,监听 {host}:{port}")try:while True:# 接收数据data, addr = udp_socket.recvfrom(1024)message = data.decode('utf-8')print(f"收到来自 {addr} 的消息: {message}")# 可选:发送回复if message.lower() == 'hello':reply = "Hello from UDP Receiver!"udp_socket.sendto(reply.encode('utf-8'), addr)except KeyboardInterrupt:print("接收端被用户中断")except Exception as e:print(f"接收错误: {e}")finally:udp_socket.close()print("UDP接收端已关闭")if __name__ == "__main__":udp_receiver()
1.3.4 UDP广播
def udp_broadcast_sender(port=9999):"""UDP广播发送端"""# 创建UDP socketudp_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)# 设置广播选项udp_socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)# 广播地址broadcast_address = '<broadcast>'try:while True:# 获取用户输入message = input("请输入广播消息 (输入 'exit' 退出): ")if message.lower() == 'exit':break# 发送广播udp_socket.sendto(message.encode('utf-8'), (broadcast_address, port))print(f"已广播: {message}")except Exception as e:print(f"广播错误: {e}")finally:udp_socket.close()print("广播发送端已关闭")def udp_broadcast_receiver(port=9999):"""UDP广播接收端"""udp_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)# 绑定到所有接口udp_socket.bind(('', port))print(f"广播接收端启动,监听端口 {port}")try:while True:data, addr = udp_socket.recvfrom(1024)message = data.decode('utf-8')print(f"收到来自 {addr} 的广播: {message}")except KeyboardInterrupt:print("广播接收端被用户中断")except Exception as e:print(f"接收错误: {e}")finally:udp_socket.close()print("广播接收端已关闭")if __name__ == "__main__":# 需要在不同终端运行接收端和发送端import sysif len(sys.argv) > 1 and sys.argv[1] == 'receiver':udp_broadcast_receiver()else:udp_broadcast_sender()
二、多任务编程
多任务编程允许程序同时执行多个任务,提高程序效率和响应性。Python中主要通过多线程和多进程实现。
2.1 多线程编程
import threading
import timedef worker(name, delay):"""简单的 worker 函数"""print(f"线程 {name} 开始执行")time.sleep(delay)print(f"线程 {name} 执行完成,延迟 {delay} 秒")# 创建多个线程
threads = []
for i in range(5):t = threading.Thread(target=worker, args=(f"Thread-{i}", i))threads.append(t)t.start()# 等待所有线程完成
for t in threads:t.join()print("所有线程执行完成")
2.2 线程同步
import threading# 使用锁进行同步
counter = 0
lock = threading.Lock()def increment_counter():global counterfor _ in range(100000):with lock: # 使用上下文管理器自动获取和释放锁counter += 1# 创建多个线程增加计数器
threads = []
for _ in range(10):t = threading.Thread(target=increment_counter)threads.append(t)t.start()for t in threads:t.join()print(f"最终计数器值: {counter} (应为 1000000)")
2.3 多进程编程
import multiprocessing
import timedef cpu_intensive_task(n):"""CPU密集型任务"""result = 0for i in range(n):result += i * ireturn resultif __name__ == "__main__":# 创建进程池with multiprocessing.Pool(processes=4) as pool:# 并行执行任务results = pool.map(cpu_intensive_task, [10000000] * 8)print(f"计算结果: {results}")
总结
本文介绍了Python网络编程和多任务编程的基础知识:
- 网络编程基础:IP地址、端口和编解码
- TCP编程:面向连接的可靠通信,适合需要数据完整性的场景
- UDP编程:无连接的快速通信,适合实时性要求高的场景
- 多任务编程:通过多线程和多进程提高程序效率
掌握这些知识后,你可以开发各种网络应用,从简单的客户端/服务器程序到复杂的分布式系统。在实际开发中,根据需求选择合适的协议和并发模型至关重要。