我已经看到HTTP请求的文本表示是什么,但DNS请求是什么样的？数据中的哪个位置是您要查找的URL的位置？另外,响应是如何格式化的？
解决方法
这是来自Wireshark的DNS查询的原始转储.
DNS部分以24 1a开头：
0000 00 00 00 00 00 00 00 00 00 00 00 00 08 00 45 00 ........ ......E. 0010 00 3c 51 e3 40 00 40 11 ea cb 7f 00 00 01 7f 00 .<Q.@.@. ........ 0020 00 01 ec ed 00 35 00 28 fe 3b 24 1a 01 00 00 01 .....5.( .;$..... 0030 00 00 00 00 00 00 03 77 77 77 06 67 6f 6f 67 6c .......w ww.googl 0040 65 03 63 6f 6d 00 00 01 00 01 e.com... ..
以下是细分：
Domain Name System (query) [Response In: 1852] Transaction ID: 0x241a Flags: 0x0100 (Standard query) 0... .... .... .... = Response: Message is a query .000 0... .... .... = Opcode: Standard query (0) .... ..0. .... .... = Truncated: Message is not truncated .... ...1 .... .... = Recursion desired: Do query recursively .... .... .0.. .... = Z: reserved (0) .... .... ...0 .... = Non-authenticated data OK: Non-authenticated data is unacceptable Questions: 1 Answer RRs: 0 Authority RRs: 0 Additional RRs: 0 Queries www.google.com: type A,class IN Name: www.google.com Type: A (Host address) Class: IN (0x0001)
响应,再次从24 1a开始：
0000 00 00 00 00 00 00 00 00 00 00 00 00 08 00 45 00 ........ ......E. 0010 00 7a 00 00 40 00 40 11 3c 71 7f 00 00 01 7f 00 .z..@.@. <q...... 0020 00 01 00 35 ec ed 00 66 fe 79 24 1a 81 80 00 01 ...5...f .y$..... 0030 00 03 00 00 00 00 03 77 77 77 06 67 6f 6f 67 6c .......w ww.googl 0040 65 03 63 6f 6d 00 00 01 00 01 c0 0c 00 05 00 01 e.com... ........ 0050 00 05 28 39 00 12 03 77 77 77 01 6c 06 67 6f 6f ..(9...w ww.l.goo 0060 67 6c 65 03 63 6f 6d 00 c0 2c 00 01 00 01 00 00 gle.com. .,...... 0070 00 e3 00 04 42 f9 59 63 c0 2c 00 01 00 01 00 00 ....B.Yc .,...... 0080 00 e3 00 04 42 f9 59 68 ....B.Yh
分解：
Domain Name System (response) [Request In: 1851] [Time: 0.000125000 seconds] Transaction ID: 0x241a Flags: 0x8180 (Standard query response,No error) 1... .... .... .... = Response: Message is a response .000 0... .... .... = Opcode: Standard query (0) .... .0.. .... .... = Authoritative: Server is not an authority for domain .... ..0. .... .... = Truncated: Message is not truncated .... ...1 .... .... = Recursion desired: Do query recursively .... .... 1... .... = Recursion available: Server can do recursive queries .... .... .0.. .... = Z: reserved (0) .... .... ..0. .... = Answer authenticated: Answer/authority portion was not authenticated by the server .... .... .... 0000 = Reply code: No error (0) Questions: 1 Answer RRs: 3 Authority RRs: 0 Additional RRs: 0 Queries www.google.com: type A,class IN Name: www.google.com Type: A (Host address) Class: IN (0x0001) Answers www.google.com: type CNAME,class IN,cname www.l.google.com Name: www.google.com Type: CNAME (Canonical name for an alias) Class: IN (0x0001) Time to live: 3 days,21 hours,52 minutes,57 seconds Data length: 18 Primary name: www.l.google.com www.l.google.com: type A,addr 66.249.89.99 Name: www.l.google.com Type: A (Host address) Class: IN (0x0001) Time to live: 3 minutes,47 seconds Data length: 4 Addr: 66.249.89.99 www.l.google.com: type A,addr 66.249.89.104 Name: www.l.google.com Type: A (Host address) Class: IN (0x0001) Time to live: 3 minutes,47 seconds Data length: 4 Addr: 66.249.89.104
编辑：
请注意,如果您真正的问题是“如何编写DNS服务器？”,那么有两个合适的答案：
>不要这样做,使用现有的,例如bind或dnsmasq
>阅读spec
编辑(2)：
请求是在linux机箱上使用主机发送的：
host www.google.com
如果您使用的是Windows,则可以使用nslookup
nslookup www.google.com
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