LocateRegistry.createRegistry(10999);
默认当调用代码的进程停掉，端口释放，服务停止。

可是当代码被调用两次：
    LocateRegistry.createRegistry(10999);
    LocateRegistry.createRegistry(10999);

 java.rmi.server.ExportException: internal error: ObjID already in use
    at sun.rmi.transport.ObjectTable.putTarget(ObjectTable.java:169)
    at sun.rmi.transport.Transport.exportObject(Transport.java:74)
    at sun.rmi.transport.tcp.TCPTransport.exportObject(TCPTransport.java:229)
    at sun.rmi.transport.tcp.TCPEndpoint.exportObject(TCPEndpoint.java:393)
    at sun.rmi.transport.LiveRef.exportObject(LiveRef.java:129)
    at sun.rmi.server.UnicastServerRef.exportObject(UnicastServerRef.java:190)
    at sun.rmi.registry.RegistryImpl.setup(RegistryImpl.java:92)
    at sun.rmi.registry.RegistryImpl.<init>(RegistryImpl.java:78)
    at java.rmi.registry.LocateRegistry.createRegistry(LocateRegistry.java:186)

方法：
    Registry registry = LocateRegistry.createRegistry(10999);
    UnicastRemoteObject.unexportObject(registry, true);
    LocateRegistry.createRegistry(10999);

不过，这样的方法是异步的，因为在测试时，碰到了端口被占用错误。