get IP dynamically

[j.gohel]

Hello all
I am making a chat application in which i use JSP and Servlet
Now I have provided the normal login page that is in swing that calls the servlet and does the authentication with the server against databse

Now i would only be giving the swing gui to the client in a jar
But the IP that i pass while compiling and making a jar of swing client is static

Now every time the server changes i need to recompile the class file
Taking the case of yahoo that must be having many servers but the client never needs to specify the IP

Is there any way that my client can get the IP without me having to recompile it everytime before giving it to the client

Thanks
Regards
Jignesh

[Belisarius]

InetAddress.getLocalHost();

[webcomplete.com]

Im not sure if your question is clear - but I guess you mean that the client need to point to the server's ip? so that you can login and perform transactions?

if thats the case, why dont you just use a domain name? you can make a domain name point to an ip via DNS. And if your client needs to go through a certain port, then you can connect your client like: "chat.mydomain.com:8888"

and when the ip changes, you just need to update the domain to the new ip instead of recompiling the program and forcing everyone to download a new copy of the client.

note however, most dns updates takes as little as 1 hour to as much as 48 hours to propagate worldwide - but surely this is better than recompiling a new client. on the other hand, your server should really be on a static ip. or you can get a hosting service for java with sql server and static ip for about 10 dollars a month.

[Belisarius]

Ah, if you need to find the server, that's what things like Jini are for; automatic serivce discovery. Damned if I know how to make it work though. It's a bit more robust than just pointing it at a DNS address, but it's a bit more complicated too.

[DJMaze]

If you have a website you could also host a file or redirect on that which client reads and your server updates.

So if your IP changes it updates mydomain.com/server.ip
Then the client reads mydomain.com/server.ip and use the provided ip to connect.

Another option is to use a HTTP/1.0 status code
write for example a PHP script that does:

PHP Code:

<?php
// Many pre-HTTP/1.1 user agents do not understand the 303 so we use 302
header('HTTP/1.0 302 Found');
header('Location: 123.45.67.89:8888');

Ofcourse the client should understand the 302 and react on that.

[Belisarius]

That *really* won't work for him - he was needing something that he can put in a compiled class to discover the server (needless to say, you can't simply insert PHP into a Java class). If he already knew the address (DNS or IP), he wouldn't be having these problems. Unless he was talking about finding his own IP, we've been working on the assumption that he has no clue as to where his server is located any given day. Your solution only works if you know the DNS address, which isn't an assumption here.