«

i have a public hostname "a" (not my machine name)on internet and my
ip is xx.xx.xx.xx;
the problem is other people can get my ip through hostname.but if he
try to get my hostname through ip he always failed.
the case above is in my program (i make it) ,what can i do for this?

> i have a public hostname "a" (not my machine name)on internet and my
> ip is xx.xx.xx.xx;
> the problem is other people can get my ip through hostname.but if he
> try to get my hostname through ip he always failed.
> the case above is in my program (i make it) ,what can i do for this?

Are you using InetAddress.getHostName()?

String getHostName()
Gets the host name for this IP address.

If you are, it could be a DNS or router issue that isn't propagating
your host-IP mapping?

Rob

dxuranus wrote:

> i have a public hostname "a" (not my machine name)on internet and my
> ip is xx.xx.xx.xx;
> the problem is other people can get my ip through hostname.but if he
> try to get my hostname through ip he always failed.

Sounds as if something's screwy with reverse DNS lookup. That /might/ be an
error, or more likely is just a result of how your ISP/'DNS/etc works. This
isn't really Java-related at all. Talk to whoever provides your DNS entry
(whoever it is that provides the lookup from the domain name, xxx.yyy.zzz, to
your numeric IP address -- which is probably whoever you paid to register your
domain name).

-- chris

Chris Uppal wrote:
> dxuranus wrote:
>
> > i have a public hostname "a" (not my machine name)on internet and my
> > ip is xx.xx.xx.xx;
> > the problem is other people can get my ip through hostname.but if he
> > try to get my hostname through ip he always failed.
>
> Sounds as if something's screwy with reverse DNS lookup. That /might/ be an
> error, or more likely is just a result of how your ISP/'DNS/etc works. This
> isn't really Java-related at all. Talk to whoever provides your DNS entry
> (whoever it is that provides the lookup from the domain name, xxx.yyy.zzz, to
> your numeric IP address -- which is probably whoever you paid to register your
> domain name).
>
> -- chris
ye that's right it's about dns reverse.i think it can be done by
program (because qmail can)
..but i do't know how?

dxuranus wrote:
> Chris Uppal wrote:
>> dxuranus wrote:
>>
>>> i have a public hostname "a" (not my machine name)on internet and my
>>> ip is xx.xx.xx.xx;
>>> the problem is other people can get my ip through hostname.but if he
>>> try to get my hostname through ip he always failed.
>> Sounds as if something's screwy with reverse DNS lookup. That /might/ be an
>> error, or more likely is just a result of how your ISP/'DNS/etc works. This
>> isn't really Java-related at all. Talk to whoever provides your DNS entry
>> (whoever it is that provides the lookup from the domain name, xxx.yyy.zzz, to
>> your numeric IP address -- which is probably whoever you paid to register your
>> domain name).
>>
>> -- chris
> ye that's right it's about dns reverse.i think it can be done by
> program (because qmail can)
> .but i do't know how?
>

I'm not sure how qmail fits into this - are you not running it on the
same machine?

You might want to have a look at http://www.dnsstuff.com/ and see what
DNS records have been configured.

dxuranus wrote:

> ye that's right it's about dns reverse.i think it can be done by
> program (because qmail can)

To do it programmatically from Java, see Robert's earlier reply.

If you mean that people in other parts of the world can do the reverse lookup
(using qmail -- whatever that is) but that the same people can't use Java to do
it, then I have no idea what could cause that.

If you mean that /you/ can do a reverse lookup (using qmail), but that /other
people/ can't do it (using anything), then that's not so very surprising. In
this case qmail is running on the machine with the relevant IP address and is
not representative of any other machine on earth.

If you mean that you can use qmail (or something) on your local LAN, but
nothing works from elsewhere in the world, then that's just how DNS (and
networks in general) work. Talk to your system administrators -- they will be
able to explain your set-up better than I can.

If you mean that some people (out on the Net) can use qmail (or anything) to do
a reverse lookup, but that other people in different parts of the world cannot,
then that indicates a screw-up in the DNS system somewhere and there is nothing
whatever you can do about it except talk to the people who are managing your
domain name.

-- chris

Chris Uppal wrote:
> dxuranus wrote:
>
> > ye that's right it's about dns reverse.i think it can be done by
> > program (because qmail can)
>
> To do it programmatically from Java, see Robert's earlier reply.
>
> If you mean that people in other parts of the world can do the reverse lookup
> (using qmail -- whatever that is) but that the same people can't use Java to do
> it, then I have no idea what could cause that.
>
> If you mean that /you/ can do a reverse lookup (using qmail), but that /other
> people/ can't do it (using anything), then that's not so very surprising. In
> this case qmail is running on the machine with the relevant IP address and is
> not representative of any other machine on earth.
>
> If you mean that you can use qmail (or something) on your local LAN, but
> nothing works from elsewhere in the world, then that's just how DNS (and
> networks in general) work. Talk to your system administrators -- they will be
> able to explain your set-up better than I can.
>
> If you mean that some people (out on the Net) can use qmail (or anything) to do
> a reverse lookup, but that other people in different parts of the world cannot,
> then that indicates a screw-up in the DNS system somewhere and there is nothing
> whatever you can do about it except talk to the people who are managing your
> domain name.
>
> -- chris
not just qmail but dnsjava also. i am now on procesing analsys it,hope
will get result.