Autobahn|Java - Instant disconnect when attempting to connect (both on Android as well as on a PC)

[Luka Miljak]

The problem I get is very simple, yet the cause remains unknown to me. The following code does not seem to work:

import io.crossbar.autobahn.wamp.Client;
import io.crossbar.autobahn.wamp.Session;
import io.crossbar.autobahn.wamp.types.ExitInfo;

import java.util.concurrent.CompletableFuture;

public class Main {

   public static void main(String[] args) {

      final String url = "ws://localhost:8080";
      final String realm = "realm";

      Session session = new Session();

      session.addOnJoinListener((ses, details) -> System.out.println("Joined"));
      session.addOnDisconnectListener((ses, clean) -> System.out.println("Disconnected"));
      session.addOnLeaveListener((ses, clean) -> System.out.println("Left"));
      session.addOnConnectListener((ses) -> System.out.println("Connected"));

      Client client = new Client(session, url, realm);

      CompletableFuture<ExitInfo> connection = client.connect();
      connection.join();
      System.out.println("Exiting");
   }
}

The dependency I included in my pom.xml is as follows:

<dependency>
    <groupId>io.crossbar.autobahn</groupId>
    <artifactId>autobahn-java</artifactId>
    <version>18.5.1</version>
</dependency>

When running this code, my console logs are:

Aug 02, 2018 1:16:59 PM io.crossbar.autobahn.wamp.transports.NettyWebSocketClientHandler
INFO: WebSocket Client disconnected!
Left
Disconnected
Exiting

At this point, the program has not terminated yet. Meaning that there still must be some unknown Thread running in the background.
Furthermore, if I try to connect to the router using Autobahn|JS, it works just fine.

The Crossbar router does not give any logs whatsoever. However, attempting using the Go Nexus Router, I get the following log: "Error attaching to router: did not receive HELLO: receive channel closed"

Some help with this problem would be appreciated.

[Omer Akram]

Hi!

This is unrelated to autobahn, rather the way java's async programming works so to fix it, instead of connect.join() do connection.get() and your program should work.

[Luka Miljak]

Hmm, I've replaced my connection.join() with the following code:

try {
   connection.get();
} catch (InterruptedException e) {
   e.printStackTrace();
} catch (ExecutionException e) {
   e.printStackTrace();
}

and I still get the exact same logs. Getting anything different would be strange as I thought that future.join() does the same as future.get() with the difference that "join" throws unchecked exceptions and "get" throws checked exceptions, requiring you to surround it by a try-catch block.

Furthermore, I've also tried using a callback as such:

connection.thenAccept(exitInfo -> {
   System.out.println("Exiting");
});
new Scanner(System.in).nextLine();

which also gives me the same result. (I added the Scanner line to wait for a newline, as the program immediately terminates if that doesn't happen.

[Tobias Oberstein]

Hi,

>>> Some help with this problem would be appreciated.

as mentioned, your problems are async programming related, not
autobahn-java .. I would read a little into Java 8 and Future etc

also, try our getting started

https://github.com/crossbario/autobahn-java#getting-started

and move from there ..

cheers,
/Tobias

[Omer Akram]

One suggestion, your url should be as below (not the trailing /ws) and please make sure your realm name refers to whats configured in Crossbar config.

ws://localhost:8080/ws