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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