Python:DNS客户端实现

最后更新于:2022-04-01 19:41:52

这两天在测试IPV6与DNS,晚上查了下资料,写了个DNS客户端,其中请求消息编码部分参考网上实例。 刚完成了编码,功能还没有测试。 1、代码: ~~~ #!/usr/bin/env python # -*- coding: utf-8 -*- import ConfigParser import socket import time import string import os import re import struct def dns_codec(hostname): ''' Function:请求消息编码 Input:hostname:主机名,如www.baidu.com Output: 编码后的字节流 author: socrates date:2012-12-14 ''' index = os.urandom(2) hoststr = ''.join(chr(len(x))+x for x in hostname.split('.')) data = '%s\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00%s\x00\x00\x01\x00\x01' % (index, hoststr) data = struct.pack('!H', len(data)) + data return data def dns_decode(in_sock): ''' Function:响应消息解码 Input:in_sock:接收消息的socket Output:解码后的内容 author: socrates date:2012-12-14 ''' rfile = in_sock.makefile('rb') size = struct.unpack('!H', rfile.read(2))[0] data = rfile.read(size) iplist = re.findall('\xC0.\x00\x01\x00\x01.{6}(.{4})', data) return ['.'.join(str(ord(x)) for x in s) for s in iplist] def dns_sendmsg(): ''' Function:通过socket发送DNS查询消息 Input:None Output:None author: socrates date:2012-12-14 ''' ens_client_config = ConfigParser.ConfigParser() #读取配置文件 try: ens_client_config.readfp(open('ens_client_config.ini')) except ConfigParser.Error: print 'read ens_client_config.ini failed.' #获取需要的信息 server_ip_1 = ens_client_config.get("server_info","ip_1") server_port_1 = ens_client_config.get("server_info","port_1") sockettype_1 = ens_client_config.get("server_info","sockettype_1") heartbeat_1 = ens_client_config.get("server_info","heartbeat_1") msg_1 = ens_client_config.get("server_info","msg_1") #IP类型 address_family = {True:socket.AF_INET6, False:socket.AF_INET}[':' in server_ip_1] #传输类型 socket_type = {True:socket.SOCK_STREAM , False:socket.SOCK_DGRAM}['TCP' == sockettype_1.upper()] try: sock = socket.socket(address_family, socket_type) except socket.error, e: print 'create socket return error. errno = %d, errmsg = %s' % (e.args[0], e.args[1]) #连接服务器并发送消息 try: #连接服务端 sock.connect((server_ip_1, string.atoi(server_port_1))) while True: #发送频率 time.sleep(string.atoi(heartbeat_1)) #发送消息 sock.sendall(dns_codec(msg_1)) #接收并打印消息 print dns_decode(sock) except socket.error, e: print 'connect server failed. errno = %d, errmsg = %s' % (e.args[0], e.args[1]) sock.close() if __name__ == '__main__': dns_sendmsg() ~~~ 2、配置文件: 文件名:ens_client_config.ini 内容: ~~~ [server_info] ip_1=192.168.1.1 port_1=53 sockettype_1=UDP heartbeat_1=2 msg_1=www.google.com ~~~ 3、早上测试了下UDP协议下的DNS客户端,功能正常可用。 a、wireshark抓包: 请求: ![QQ截图20121216114223](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-06-08_575793629beb2.jpg) 响应: ![QQ截图20121216114223](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-06-08_57579362bea0b.jpg) b、代码运行结果: ![QQ截图20121216114223](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-06-08_57579362e34af.jpg)
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