Akka BindException when trying to connect to remote actor: Address already in use

Question

I am experimenting with Akka remote actors, trying to establish a simple 2 player game over the network. This answer to an earlier question gave me a really good starting point but now I'm having a hard time understanding how to adapt it to my situation. ISTM that the original is connecting twice from the same client (see commented section below). What I want to do is run it twice from separate clients, but when I do I get a BindException, Address already in use. I guess that's because each time I run the code it attempts to start the server? I need a situation where I can start and stop the master actor independently of clients connecting and disconnecting. The (minimal) Akka config and exception are after the code: ``` import akka.actor._ //example from answer to https://stackoverflow.com/questions/15527193/keeping-references-to-two-actors // by Patrick Nordwall case object JoinMsg case class Msg(s: String) class Server extends Actor { def receive = { case JoinMsg => println("got pl…

Accepted Answer

When running several instances on same machine you need to configure different ports for them. In this example it is only the server that needs a know port (9000). For the clients you can use 0 for a random available port.

Define another configuration file for the clients. `client.conf`:

```
akka {
  actor {
    provider = "akka.remote.RemoteActorRefProvider"
  }
  remote {
    transport = "akka.remote.netty.NettyRemoteTransport"
    netty {
      hostname = "localhost"
      port = 0
    }
 }
}
```

Start the `ActorSystem` in the clients with this configuration:

```
import com.typesafe.config.ConfigFactory
val system = ActorSystem("Game", ConfigFactory.load("client"))
```

In the clients you will lookup the server with:

```
val server = system.actorFor("akka://Game@localhost:9000/user/server")
```

Akka BindException when trying to connect to remote actor: Address already in use

Solution

Problem