# Get host by addr

**URL:** <https://www.ruby-forum.com/t/get-host-by-addr/111837>\
**Category:** Ruby\
**Created:** [August 12, 2007, 12:01am UTC](https://www.ruby-forum.com/t/get-host-by-addr/111837 "2007-08-12T00:01:41Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Nikos\_Kanellopoulos](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/c5a1d2/32.png) [@Nikos\_Kanellopoulos](https://www.ruby-forum.com/u/Nikos_Kanellopoulos)\
**Post date:** [August 12, 2007, 12:01am UTC](https://www.ruby-forum.com/t/get-host-by-addr/111837/1 "2007-08-12T00:01:41Z")

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Hello everybody.  
I am trying to do something simple.  
I have an IP address and need to do a reverse DNS lookup.  
However, I consistently get a “host not found” error.  
I have tried this in at least 2 different machines.

What am I doing wrong?

nk@livaditis: ~ $ irb  
irb(main):001:0\> require ‘socket’  
=\> true  
irb(main):002:0\> Socket.gethostbyaddr(“75.126.252.65”)  
SocketError: host not found  
from (irb):2:in `gethostbyaddr’  
from (irb):2  
from :0

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<div class="post-metadata">

**Author:** ![Nikos\_Kanellopoulos](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/c5a1d2/32.png) [@Nikos\_Kanellopoulos](https://www.ruby-forum.com/u/Nikos_Kanellopoulos)\
**Post date:** [August 12, 2007, 12:24am UTC](https://www.ruby-forum.com/t/get-host-by-addr/111837/2 "2007-08-12T00:24:42Z")

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> I have tried this in at least 2 different machines.  
> from :0

irb(main):001:0\> require ‘socket’  
=\> true  
irb(main):002:0\> Socket.getaddrinfo(‘75.126.252.65’, nil)  
=\> [[“AF\_INET”, 0, “[75.126.252.65-static.reverse.softlayer.com](http://75.126.252.65-static.reverse.softlayer.com)”,  
“75.126.252.65”, 2, 1, 6], [“AF\_INET”, 0,  
“[75.126.252.65-static.reverse.softlayer.com](http://75.126.252.65-static.reverse.softlayer.com)”, “75.126.252.65”, 2, 2,  
17],  
[“AF\_INET”, 0, “[75.126.252.65-static.reverse.softlayer.com](http://75.126.252.65-static.reverse.softlayer.com)”,  
“75.126.252.65”, 2, 3, 0]]  
irb(main):003:0\>

---

<div class="post-metadata">

**Author:** ![Nikos\_Kanellopoulos](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/c5a1d2/32.png) [@Nikos\_Kanellopoulos](https://www.ruby-forum.com/u/Nikos_Kanellopoulos)\
**Post date:** [August 12, 2007, 12:58am UTC](https://www.ruby-forum.com/t/get-host-by-addr/111837/3 "2007-08-12T00:58:44Z")

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2007/8/12, Felix W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> > I have tried this in at least 2 different machines.  
> > from :0  
> > “75.126.252.65”, 2, 3, 0]]  
> > irb(main):003:0\>

Nice! This works fine in irb.  
However, it fails to do the reverse lookup from within my rails  
application.  
It just returns the IP as the host name. Strange…