Why does java rmi keep connecting to 127.0.1.1. When ip is 192.168.X.X?

Question

I have a java rmi application i simply do:

Client:

Registry registry = LocateRegistry.getRegistry("localhost");
costApi = (CostApi) registry.lookup("server.CostApi");

Everything works fine when I host the server at localhost. When I start the same program at another machine withing the local network, at 192.168.x.x and change to:

Client:

Registry registry = LocateRegistry.getRegistry("192.168.x.x");
costApi = (CostApi) registry.lookup("server.CostApi");

it does not work anymore and it fails with a very strange error:

java.rmi.ConnectException: Connection refused to host: 127.0.1.1; nested exception is: 
    java.net.ConnectException: Connection refused
    at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
    at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
    at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:129)
    at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:194)
    at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:148)
    at com.sun.proxy.$Proxy0.dataCost(Unknown Source)
    at billing.data.DataBiller.performBilling(DataBiller.java:57)
    at billing.data.DataBiller.consumeMessage(DataBiller.java:46)
    at general.templates.RabbitWorker.run(RabbitWorker.java:124)
    at java.lang.Thread.run(Thread.java:744)
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)

I'm not even trying to connect to 127.0.1.1 but to 192.168.x.x, how do I solve this? I prefer to use java code only and not modify my machine with config files. I'm using linux

Answer 1

This is usually caused by a misconfiguration. Check your /etc/hosts file to ensure that:

• localhost maps to 127.0.0.1
• your real hostname maps to your real host address

Some Linux distributions are known to have this back to front.

If the problem persists, try setting java.rmi.server.hostname at the server to the IP address the client should use when executing remote method calls. It needs to be set before you export any remote objects, including the Registry.

The problem is caused by the IP address embedded in the stub, which ultimately comes from something like InetAddress.getLocalAddress(), which is fallible as above. It is overridden by java.rmi.server.hostname.

This is item A.1 in the FMI FAQ, but note that the item is mistitled. It doesn't happen during lookup(), it happens when you call a remote method on the resulting stub.