Using Twisted in Python to Implement DNS Resolution and Caching

Preparation work for environmental construction: 1. Install Python: First, ensure that the Python interpreter has been installed, which can be accessed from the official website（ https://www.python.org ）Download the latest version of Python and follow the installation prompts to complete the installation. 2. Install Twisted: Twisted is an event driven network framework that can be used to implement asynchronous Web application. You can use the following command to install Twisted through Python's package manager pip: pip install twisted Dependent class libraries: 1. twisted. names: This is the DNS resolution library in Twisted, which includes related functions for DNS queries and responses. The complete sample code is as follows: python from twisted.internet import reactor, defer from twisted.names import client, dns class MyDNSResolver(object): def __init__(self): self.cache = {} def query(self, name): if name in self.cache: print(f"Cache hit: {name}: {self.cache[name]}") return defer.succeed(self.cache[name]) print(f"Cache miss: {name}") d = client.lookupAddress(name) d.addCallback(self._cache_result, name) return d def _cache_result(self, result, name): if result: self.cache[name] = result return result if __name__ == "__main__": resolver = MyDNSResolver() reactor.installResolver(resolver) def print_result(result): for r in result: print(r) reactor.stop() d = resolver.query("www.google.com") d.addCallback(print_result) reactor.run() Code Explanation: Firstly, we created a MyDNSResolver class that inherits from the twisted. names. client. Resolver class. In this class, we define a cache attribute 'self. cache' to store query results. The 'query' method is used to perform DNS queries. It first checks whether the query results exist in the cache, and if so, returns the cached results directly. If it does not exist, use the 'client. lookupAddress' method for a real DNS query and cache the results after the query is completed. 3. ` print_ The 'result' method is used to print the query results and stop the Twisted event loop after the results are printed. 4. In the`__ Main__` In, we created a MyDNSResolver instance and set it as the default DNS parser using 'reactor. installResolver (resolver)'. 5. Then, we use the 'resolver. query' method to query DNS, and call 'print' after the query is completed_ The 'result' method prints the query results. Finally, we call 'reactor. run()' to start the Twisted event loop. Summary: By using Twisted's twisted. names library, we can easily implement DNS parsing and caching functions. Twisted provides an event driven network framework, enabling us to build high-performance, asynchronous Web application. In practical applications, Twisted can provide more functions for more complex network application development.