UnknownHostException for server java

Question

I am not able to connect to an remote known server through Java code; the exception while connecting is java.net.NoRouteToHostException: No route to host.

But strangely, I am able to connect to same server through ssh.

Details: Simple Java client when tries to establish connection with Java standalone server, while conneting the exception occurs at following statement:

Socket socket = new Socket(ServerIP ServerPort);

The port needed is open on server so that externally request can come in.

Again the following is returns false

InetAddress.getByName(SERVER_IP).isReachable(1000)

The Server is running on Fedora, Java 5.

FYI: Java cannot resolve DNS address from AIX: UnknownHostException is almost same to my question, but somehow this is not AIX related; moreover I feel the issue to be more of Network or firewall issue.

Please guide me.

Answer 1

I suggest testing things to narrow down the problem area:

1. can you telnet to the host/port?
2. Can Java connect to any other host/port successfully?
3. Are you using host names or IP addresses - try which ever one you are not using.
4. Is either computer running a firewall?

Answer 2

Additionally you should also check your .ssh/config file, maybe there is a different Hostname defined for the name you use on the command line.

Answer 3

What about /etc/hosts? Maybe it interferes somehow? Just a guess.