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RST报文段的意义

news 2025/9/18 6:14:58

客户端代码，服务端代码如下

客户端代码

import socketSERVER_ADDR = '127.0.0.1'
PORT        = 18000
CHUNK_SIZE  = 1024 * 4def main():""" echo 客户端: 基于 AF_INET domain and TCP type 的 socket """# socket -> s.connect -> s.sendall -> s.shutdown -> loop s.recv -> s.closewith socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:s.connect((SERVER_ADDR, PORT))s.sendall(b"hello")s.shutdown(socket.SHUT_WR)  # if without this line code, the server and client will be deadlocked!response = b""while data := s.recv(CHUNK_SIZE):response += dataprint(response.decode())if __name__ == "__main__":main()

服务端代码

import socketHOST = '0.0.0.0'
PORT = 18000
BACKLOG = 16
CHUNK_SIZE = 1024 * 4def handle_client(conn, addr):with conn:print(f"{addr[0]}:{addr[1]}", flush=True, end=' ')request = b""while data := conn.recv(CHUNK_SIZE):request += dataprint(request.decode(), flush=True)conn.sendall(request)def main():""" echo 服务器: 基于 AF_INET domain and TCP type 的 socket """# socket -> s.bind -> s.listen -> s.accept -> s.closewith socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)s.bind((HOST, PORT))s.listen(BACKLOG)print(f"Listening on {HOST}:{PORT}\n", flush=True) try:while True:conn, addr = s.accept()handle_client(conn, addr)except KeyboardInterrupt:print("\nServer shutting down...")if __name__ == "__main__":main()

运行结果如下

删除客户端一行代码就会发生死锁，如下

s.shutdown(socket.SHUT_WR)  # if without this line code, the server and client will be deadlocked!

死锁发生的时候，按下Ctrl + C 结束客户端的运行，则有以下过程

客户端的内核开始清理客户端的socket资源，首先向服务端发送一个FIN报文

服务端内核收到FIN报文，然后服务端从recv返回，打印数据，然后sendall发送数据

客户端收到服务端发送的数据，不处理，向客户端发送RST报文，表示客户端的socket已经不存在，不要再发送数据了

服务端收到RST报文，关闭conn socket，重新回到main函数的while循环中

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