Python DNS客户端实现代码

#!/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.jb200.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 = '%sx01x00x00x01x00x00x00x00x00x00%sx00x00x01x00x01' % (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.x00x01x00x01.{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() 

[server_info]
ip_1=192.168.1.1
port_1=53
sockettype_1=UDP
heartbeat_1=2
msg_1=www.google.com