Python:DNS客户端实现

  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