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 = "%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()
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:
响应:
b、代码运行结果: