I have a very simple rmi client / server application. I don't use the "rmiregistry" application though, I use this to create the server:
server = new RemoteServer();
registry = LocateRegistry.createRegistry(PORT);
registry.bind("RemoteServer", server);
The client part is:
registry = LocateRegistry.getRegistry(IPADDRESS, PORT);
remote = (IRemoteServer) registry.lookup("RemoteServer");
Here is the fascinating problem: The application works perfectly when both server and client are running in my (private) local network. As soon as I put the server on a public server, the application hangs for a minute, then gives me the following error:
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.ConnectException: Connection refused to host: 192.168.x.y; nested exception is:
java.net.ConnectException: Connection timed out: connect
at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source ... (the rest is truncated)
The key I think is that the client (running on my private network) cannot connect to myself (my address is 192.168.x.y where x.y is some other numbers, but the real error message shows my ip address listed there)
If I kill the rmi server on the public internet, then I instantly get a "connection refused to host: a.b.c.d") message, so I know that something at the server end is at least working.
Any suggestions?
EDIT: just to make this a little more clear: 192.168.x.y is the client address, a.b.c.d is the server address. The stacktrace shows the client cannot connect to the client.
Try running the server with this parameter for the virtual machine:
-Djava.rmi.server.hostname=hostname_of_the_server
192.168.* contains private IP addresses (as does 10.*). These will not be routed on the open internet. You need to make sure that you are using an public IP address for the server, and any firewalls (including NAT) are configured for access. You can do a quick check with telnet on the required port.
I would believe that the server tries to open a socket back to the client and it fails, and the exception is a bit unclear on its wording.
RMI is not very NAT-friendly, IIRC.
Related
I am playing with the code https://cs.lmu.edu/~ray/notes/javanetexamples/#chat at the moment.
In the line
var client = new ChatClient(args[0]);
of the clients' main method you pass a host name to the constructor.
I am still getting a "ConnectException: connection refused" trying to connect to my server as a client over the internet (with my public IP), whereas I can connect to it locally (with "localhost"). I have checked the firewall, all ports and the server itself, but still getting it. The ping to my IP works, but the connection is being refused.
Is it possible for me to connect as a client over the internet from my laptop to the server running at my laptop?
The trace:
Exception in thread "main" java.net.ConnectException: Connection refused: connect
at java.base/sun.nio.ch.Net.connect0(Native Method)
at java.base/sun.nio.ch.Net.connect(Net.java:503)
at java.base/sun.nio.ch.Net.connect(Net.java:492)
at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:333)
at java.base/java.net.Socket.connect(Socket.java:648)
at java.base/java.net.Socket.connect(Socket.java:597)
at java.base/java.net.Socket.<init>(Socket.java:520)
at java.base/java.net.Socket.<init>(Socket.java:294)
at ChatClient.run(ChatClient.java:71)
at ChatClient.main(ChatClient.java:97)
So, calling client.run() the exception occurs when trying to open a socket at the passed IP address at
var socket = new Socket(serverAddress, 50000);
and I use the port 50000 for both.
It is extremely unlikely that you would be able to connect directly to your computer from the internet without extra work.
Minimally you would need to do port forwarding in your router to redirect all connections to port 59001 to your machine.
In suggest using something like ngrok for this instead:
ngrok http 59001
and now you should be able to connect to your service
var socket = new Socket("http://CUSTOM_URL_PROVIDED_BY_NGROK.ngrok.io", 59001);
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
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.
I just ran into the same issue. I'm doing something very similar to what you are doing. What I noticed was that the first time I ran the client program, and it failed ( by design of the firewall test ) - that it failed with an error message showing the actual ip address of the host that I originally specified ( the 192.168.x.x address ), but all subsequent failures show that it is failing to make a connection to 127.0.0.1. Currently I'm suspecting some kind of caching on the client - has the JVM marked that ip address as never accessible again and it's refusing to ever try to connect to it again?
UPDATE: In my case, the JVM on the RMI Server side was not able to properly set the java.rmi.server.hostname property at JVM startup. This property was being left as null. When clients connect to a specific RMI Registry and ask for a stub to a particular named object, they receive a stub containing the ip address of the remote machine where the actual object can be found. The RMI server copies the contents of the java.rmi.server.hostname property into the stubs it returns to clients, so if the java.rmi.server.hostname property is "" and it copies that to each stub it creates, each stub contains a reference to remote server with an IP address of "". By default the client jvm reacts to this by attempting to connect to the server object on the localhost, 127.0.0.1. To work around the problem, try this line of code before exporting any remote objects on the server side:
System.setProperty( "java.rmi.server.hostname", "192.168.RMIServer.IP" ) ;
This property will be automatically copied to all remote stubs exported on that server, and clients who receive that stub should then be able to reach the remote server ( assuming any firewalls are configured correctly ).
while trying to create a new connection to rabbitmq running on a different server, I got the following error:
java.io.IOException
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:106)
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:102)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:124)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:406)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:516)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:533)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error; reason: java.net.SocketException: Connection reset
at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:67)
at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:33)
at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:343)
at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:216)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:118)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.io.BufferedInputStream.fill(Unknown Source)
at java.io.BufferedInputStream.read(Unknown Source)
at java.io.DataInputStream.readUnsignedByte(Unknown Source)
at com.rabbitmq.client.impl.Frame.readFrom(Frame.java:95)
at com.rabbitmq.client.impl.SocketFrameHandler.readFrame(SocketFrameHandler.java:131)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:533)
Steps taken :
rabbitmq is running on the server.
server is specified
default port is specified
lsof -i tcp:5672
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
beam.smp 3084 rabbitmq 15u IPv6 18611 0t0 TCP *:amqp (LISTEN)
rabbitmqctl list_connections
Listing connections ...
guest client_server 55765 running
...done.
netstat -tapnl | grep 5672
tcp 0 0 0.0.0.0:15672 0.0.0.0:* LISTEN 3084/beam.smp
tcp 0 0 0.0.0.0:55672 0.0.0.0:* LISTEN 3084/beam.smp
tcp 0 0 :::5672 :::* LISTEN 3084/beam.smp
One of the possible reasons is that user you are connecting with to RabbitMQ has no rights to access to virtual hosts.
You can check this using Management Plugin (Admin tab).
Do not specify the default port as you have mentioned in your steps.
If you have not created virtual host on the actual server, where you are trying to connect, Do create a virtual host and give it admin permision.
Set the virtual host on the factory before creating the new connection, like factory.setVirtualHost("VIRTUAL_HOST_NAME_ON_SERVER");
Make sure username on the server on which you are trying to connect is Admin and have access to the Virtual Host you just created.
Specify your username and password along with virtual host, while getting the connection.
Start your application in Debug Mode, and check if it now passes, factory.newConection();
This should make your things work.
Got the same exception, and it worked for me.
If it still does not work paste your code snippet.
Check the host and port value
In application.properties
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest
See RabbitMQ site is running on port 15672 whereas in code using amqp protocol.
You can check if the SSL/TLS support is enabled. Then use the instruction useSslProtocol :
ConnectionFactory factory = new ConnectionFactory();
factory.useSslProtocol();
I got Unable to connect to AMQP server error when create a new connection. It was confirmed that it was a problem with the firewall. I solved it by command systemctl stop firewalld.
I wrote server and client on Java using Netty.When i run client on my PC it works just fine. When i am trying to run client on other PC it throws me:
java.net.ConnectException: connection timed out
at org.jboss.netty.channel.socket.nio.NioClientSocketPipelineSink$Boss.processConnectTimeout(NioClientSocketPipelineSink.java:391)
at org.jboss.netty.channel.socket.nio.NioClientSocketPipelineSink$Boss.run(NioClientSocketPipelineSink.java:289)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
17-Sep-2012 10:58:55 AM org.jboss.netty.channel.SimpleChannelHandler
What is the reason of this?
Check the connection parameters.
Is the server visible from another client? (try pinging the server from the client).
Are there any firewalls between? Try switching them off.
Check the connection string. Make sure you aren't connecting to localhost.
Check the server configuration. Does it listen on the proper network interface.
If you check everything and it seems OK. Post the network connection code here.
Happy coding :)
When I call, the service's method, I have Web Service Exception happening which I couldn't figure out for now.
The issue is this, I am running NetBeans 6.8 against IIS 7.0 with the Web Service written using WCF:
javax.xml.ws.WebServiceException: java.net.SocketException: Connection reset
at com.sun.xml.internal.ws.transport.http.client.HttpClientTransport.readResponseCodeAndMessage(HttpClientTransport.java:201)
at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.process(HttpTransportPipe.java:151)
at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.processRequest(HttpTransportPipe.java:83)
at com.sun.xml.internal.ws.transport.DeferredTransportPipe.processRequest(DeferredTransportPipe.java:105)
at com.sun.xml.internal.ws.api.pipe.Fiber.__doRun(Fiber.java:587)
at com.sun.xml.internal.ws.api.pipe.Fiber._doRun(Fiber.java:546)
at com.sun.xml.internal.ws.api.pipe.Fiber.doRun(Fiber.java:531)
at com.sun.xml.internal.ws.api.pipe.Fiber.runSync(Fiber.java:428)
at com.sun.xml.internal.ws.client.Stub.process(Stub.java:211)
at com.sun.xml.internal.ws.client.sei.SEIStub.doProcess(SEIStub.java:124)
at com.sun.xml.internal.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:98)
at com.sun.xml.internal.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:78)
at com.sun.xml.internal.ws.client.sei.SEIStub.invoke(SEIStub.java:107)
at $Proxy30.getTwo(Unknown Source)
at HighBeamWcfClient.Main.main(Main.java:28)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:168)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:687)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:632)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:652)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1072)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:373)
at com.sun.xml.internal.ws.transport.http.client.HttpClientTransport.readResponseCodeAndMessage(HttpClientTransport.java:198)
How to fix it?
"Connection reset" typically means that someone/something between you and the server is resetting the connection or somehow blocking it. Check that you can connect to the server on the port correctly without any issue, and that there are no firewalls in the way.
A very simple test that you can connect to the port in question is to simply telnet to it with telnet serverhostname portnum, for example telnet stackoverflow.com 80.