抱歉，您误会了。114.143.51.197没有PTR记录…因此socket.gethostbyaddr()应该引发错误…您当然需要try/except子句，用于socket.herror
>>> def lookup(addr):
... try:
... return socket.gethostbyaddr(addr)
... except socket.herror:
... return None, None, None
...
>>> name,alias,addresslist = lookup('4.2.2.2')
>>> print name
vnsc-bak.sys.gtei.net
>>> name,alias,addresslist = lookup('114.143.51.197')
>>> print name
None
>>>
DNS反向查找114.143.51.197 …请注意，它没有有效的PTR记录
[mpenning@Bucksnort ~]$ dig @8.8.8.8 -x 114.143.51.197
; <<>> DiG 9.6-ESV-R4 <<>> @8.8.8.8 -x 114.143.51.197
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 4735
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;197.51.143.114.in-addr.arpa. IN PTR
;; AUTHORITY SECTION:
114.in-addr.arpa. 1800 IN SOA ns1.apnic.net. read-txt-record-of-zone-first-dns-admin.apnic.net. 17812 7200 1800 604800 172800
;; Query time: 182 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Tue Nov 22 05:11:36 2011
;; MSG SIZE rcvd: 134
[mpenning@Bucksnort ~]$ python
Python 2.5.2 (r252:60911, Jan 24 2010, 14:53:14)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket
>>> socket.gethostbyaddr('114.143.51.197')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
socket.herror: (1, 'UnkNown host')
>>>
这就是有效PTR记录的样子……
[mpenning@Bucksnort ~]$ dig -x 4.2.2.2
; <<>> DiG 9.6-ESV-R4 <<>> -x 4.2.2.2
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61856
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 1
;; QUESTION SECTION:
;2.2.2.4.in-addr.arpa. IN PTR
;; ANSWER SECTION:
2.2.2.4.in-addr.arpa. 86400 IN PTR vnsc-bak.sys.gtei.net.
;; AUTHORITY SECTION:
2.4.in-addr.arpa. 86400 IN NS dnsauth2.sys.gtei.net.
2.4.in-addr.arpa. 86400 IN NS dnsauth1.sys.gtei.net.
2.4.in-addr.arpa. 86400 IN NS dnsauth3.sys.gtei.net.
;; ADDITIONAL SECTION:
dnsauth1.sys.gtei.net. 1800 IN A 4.2.49.2
;; Query time: 308 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Nov 22 05:10:16 2011
;; MSG SIZE rcvd: 158
[mpenning@Bucksnort ~]$ python
Python 2.5.2 (r252:60911, Jan 24 2010, 14:53:14)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket
>>> socket.gethostbyaddr('4.2.2.2')
('vnsc-bak.sys.gtei.net', [], ['4.2.2.2'])
>>>
602392714
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