CArtAgO java.rmi.ConnectException Connection refused in a distributed environment - agent

Question

I am trying to connect remotely to a JaCaMo application by CArtAgO infrastructure.
In the server my jcm file is like this:
mas testsvr {
agent bob
workspace world
platform: cartago(infrastructure)
class-path: lib // java class path
asl-path: src/agt, src/agt/inc // agent source path
}
And a client application is like this:
mas testclient {
agent alice
platform: cartago()
node n1 running # 10.0.0.14
class-path: lib // java class path
asl-path: src/agt, src/agt/inc // agent source path
}
When I've run with a server listening I got the following output:
CArtAgO Http Server running on http://127.0.1.1:3273
Jason Http Server running on http://127.0.1.1:3272
Looking for rmi://10.0.0.11/cartago_node
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:130)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:227)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:179)
at com.sun.proxy.$Proxy6.join(Unknown Source)
at cartago.infrastructure.rmi.CartagoInfrastructureLayer.joinRemoteWorkspace(CartagoInfrastructureLayer.java:62)
at cartago.CartagoService.joinRemoteWorkspace(CartagoService.java:372)
at cartago.NodeArtifact.joinRemoteWorkspace(NodeArtifact.java:99)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at cartago.ArtifactOpMethod.exec(ArtifactOpMethod.java:39)
at cartago.Artifact.doOperation(Artifact.java:407)
at cartago.Artifact.access$200(Artifact.java:32)
at cartago.Artifact$ArtifactAdapter.doOperation(Artifact.java:1275)
at cartago.WorkspaceKernel.serveOperation(WorkspaceKernel.java:1136)
at cartago.WorkspaceKernel.access$000(WorkspaceKernel.java:48)
at cartago.WorkspaceKernel$EnvironmentController.run(WorkspaceKernel.java:1477)
When I've run without a server listening the output was:
CArtAgO Http Server running on http://127.0.1.1:3273
Jason Http Server running on http://127.0.1.1:3272
java.rmi.ConnectException: Connection refused to host: 10.0.0.11; 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.newCall(UnicastRef.java:342)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Naming.java:101)
at cartago.infrastructure.rmi.CartagoInfrastructureLayer.joinRemoteWorkspace(CartagoInfrastructureLayer.java:58)
at cartago.CartagoService.joinRemoteWorkspace(CartagoService.java:372)
at cartago.NodeArtifact.joinRemoteWorkspace(NodeArtifact.java:99)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at cartago.ArtifactOpMethod.exec(ArtifactOpMethod.java:39)
at cartago.Artifact.doOperation(Artifact.java:407)
at cartago.Artifact.access$200(Artifact.java:32)
at cartago.Artifact$ArtifactAdapter.doOperation(Artifact.java:1275)
at cartago.WorkspaceKernel.serveOperation(WorkspaceKernel.java:1136)
at cartago.WorkspaceKernel.access$000(WorkspaceKernel.java:48)
at cartago.WorkspaceKernel$EnvironmentController.run(WorkspaceKernel.java:1477)
So, it shows that the client found the server but something wrong happened and the connection was refused. What is happening? Which is the default CArtAgO's connection port?

Answer 1

CArtAgO uses Java RMI, the default port is 20100. For LipeRMI connection the default port is 20101. Other constants can be checked in http://www.emse.fr/~boissier/enseignement/maop17-spring/doc/api/cartago-api/index.html?constant-values.html
It is suggested to leave server and client with no restrictions checking whether iptables INPUT, FORWARD and OUTPUT are showing ACCEPT for any case. You can use the following command:
$ iptables -L -v
On linux with JaCaMo application running you can see if the port 20100 was opened by the app (you can use ss or netstat). The response should be "LISTEN" for 20100 port
$ ss -tnl | grep 20100
or
$ netstat -tuplen | grep 20100
It is also necessary to have DNS working for the machines because the connection will use names. You may test it by command ping using machine names. From clients:
$ ping name_server
From server (ping clients)
$ ping name_client1
In case of no DNS server to solve names, it is necessary to edit /etc/hosts file. Considering the server named 'myserver_hostname' on ip 192.168.0.1 and client named 'myclient_hostname' on ip 192.168.0.2, the file on both machines, server and client, may be like this:
127.0.0.1 localhost
#127.0.1.1 myserver_hostname -- RMI will not use it anymore
192.168.0.1 myserver_hostname
192.168.0.2 myclient_hostname