Java RMI 连接异常 : Connection refused to host/timeout

Question

我正在开发一个 RMI 命令行游戏，但是每当我尝试使用我的服务时，我都会收到这样的错误:

java.rmi.ConnectException: Connection refused to host: 192.168.56.1; nested exception is: 
    java.net.ConnectException: Connection timed out: connect

这是我的 Server 的主类:

public class RMIWar {

    public static void main(String[] args) throws RemoteException, MalformedURLException  {
        try {
            Controle obj = new Controle(4);
            Registry reg = LocateRegistry.createRegistry(1099);
            System.out.println("Server is ready");
            reg.rebind("CtrlServ", obj);
        }
        catch (Exception e) {
            System.out.println("Error: " + e.toString());
        }
    }
}

我的 Client 类的主要部分:

public class RMIWarClient {
    public static void main(String[] args) throws RemoteException, MalformedURLException, NotBoundException  {
        try {
            Registry registry = LocateRegistry.getRegistry("localhost");
            ControleInt ctrl = (ControleInt) registry.lookup("CtrlServ");
            System.out.println("CtrlServ found...\n");
            BioRMI bio = new BioRMI(null, 5,5,5);
            ctrl.thRegister("Test", bio.atk, bio.def, bio.agi);

        }

        catch (Exception e) {
            System.out.println("Error: " + e);
        }
    }
}

有什么建议吗？

Answer 1

测试您的 1099 端口是否可用(这意味着被防火墙阻止)。此外，您没有提到您使用的是什么操作系统，以及您是否在执行服务器之前启动了注册表。

此 RMI tutorial解释:

Before starting the compute engine, you need to start the RMI registry. The RMI registry is a simple server-side bootstrap naming facility that enables remote clients to obtain a reference to an initial remote object.

默认情况下，注册表在端口 1099 上运行，就像您的一样。如教程所述，只需打开命令提示符(在 Windows 上)或 shell 终端(在类 UNIX 操作系统上)并键入:

对于 Windows(如果启动不可用，请使用 javaw):

start rmiregistry

Solaris 操作系统或 Linux:

rmiregistry &

更新

我注意到，按照 Oracle 的教程和我之前的一个项目，在 Server 类中，您没有将对象导出到 RMI 运行时。然后你应该编辑这些行:

Controle obj = new Controle(4);
Registry reg = LocateRegistry.createRegistry(1099);
System.out.println("Server is ready");
reg.rebind("CtrlServ", obj);

到:

Controle obj = new Controle(4);
Controle stub = (Controle) UnicastRemoteObject.exportObject(obj, 0);
Registry reg = LocateRegistry.createRegistry(1099);
System.out.println("Server is ready");
reg.rebind("CtrlServ", stub);

因为教程报告:

The static UnicastRemoteObject.exportObject method exports the supplied remote object so that it can receive invocations of its remote methods from remote clients.

此外，如果您使用同一主机进行 RMI 调用，则在 Client 类中不需要它:

Registry registry = LocateRegistry.getRegistry("localhost");

只需调用:

Registry registry = LocateRegistry.getRegistry();

因为 Oracle 报告:

The no-argument overload of LocateRegistry.getRegistry synthesizes a reference to a registry on the local host and on the default registry port, 1099. You must use an overload that has an int parameter if the registry is created on a port other than 1099.