远程管理接口UnknownHostException

Question

我正在构建的Java RMI系统遇到了问题。当我尝试连接时，我总是收到UnknownHostException。对于主机名，我尝试了我的IPv4地址、IPv6地址、"localhost“、其他一些东西，等等。我还试着输入随机的单词，看看是否有区别。没有；我得到了完全相同的错误。下面是一些代码：

public class GUI extends JFrame implements ActionListener, WindowListener
{
public static GUI Global;
private static final long serialVersionUID = 1L;
public static void main(String[] args)
{
    Global = new GUI();
    //Debugging
    System.out.println(Global.Client.getServerMessage());
}


public ClientIO()
{
    System.setProperty("java.security.policy", "file:./bin/settings.policy");
    /*if (System.getSecurityManager() == null)
    {
        System.setSecurityManager(new RMISecurityManager());
    }*/     
    System.out.println("Enter the Server IP adress (The IP adress of the machine that the server is running on)");
    try 
    {
        ClientIO.URL = new BufferedReader(new InputStreamReader(System.in)).readLine();
    } 
    catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    /*try {
        URL = java.net.InetAddress.getLocalHost().getHostName();
    } catch (UnknownHostException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }*/
}

public String getServerMessage()
{
    String szRemoteAdress = URL+"/"+WebConstants.SERVICE_NAME;
    try 
    {
        Registry registry = LocateRegistry.getRegistry(szRemoteAdress);
        EotGRemote stub = (EotGRemote) registry.lookup("EotGRemote");
        String response = stub.getTextyness();
        System.out.println("response: " + response);
    }
    catch (RemoteException | NotBoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return "";
}

public class GlobalNetIO implements Runnable
{
public static GlobalNetIO IO;
ServerSocket m_MainServerSocket;
ArrayList<Socket> m_Sockets;
ArrayList<UserNetIO> m_UserInterfaces;

public GlobalNetIO()
{
    makeRMI();
    try 
    {
        m_MainServerSocket = new ServerSocket(1111);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    //Define an ArrayList of the Socket
    m_Sockets = new ArrayList<Socket>();
}

public void makeRMI()
{
    //I don't know what this means; I'm just going to accept it
    System.setProperty("java.security.policy","file:./bin/settings.policy");
    //Might as well...
    System.setProperty("java.rmi.server.codebase", "./");
    /*if (System.getSecurityManager() == null)
        System.setSecurityManager ( new RMISecurityManager() );*/
    try
    {
        EotGRemote IO2 = new EotGRemoteIO();
        Registry registry = LocateRegistry.createRegistry(1099);
        registry.bind(WebConstants.SERVICE_NAME, IO2);
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
}

public interface EotGRemote extends Remote 
{
public String getTextyness() throws RemoteException;
}

package com.eotg.WebInterface;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import com.eotg.WebUtils.*;

public class EotGRemoteIO extends UnicastRemoteObject implements EotGRemote 
{
protected EotGRemoteIO() throws RemoteException 
{
}

@Override
public String getTextyness() {
    // TODO Auto-generated method stub
    return "It worked!";
}
}

下面是错误消息：

java.rmi.UnknownHostException: Unknown host: foo bar/Eo Nova; nested exception is: 
    java.net.UnknownHostException: foo bar/Eo Nova
    at sun.rmi.transport.tcp.TCPEndpoint.newSocket(Unknown Source)
    at sun.rmi.transport.tcp.TCPChannel.createConnection(Unknown Source)
    at sun.rmi.transport.tcp.TCPChannel.newConnection(Unknown Source)
    at sun.rmi.server.UnicastRef.newCall(Unknown Source)
    at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
    at com.eotg.Client.ClientIO.getServerMessage(ClientIO.java:57)
    at com.eotg.Client.GUI.main(GUI.java:34)
Caused by: java.net.UnknownHostException: foo bar/Eo Nova
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(Unknown Source)
    at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(Unknown Source)
    ... 7 more

Answer 1

LocateRegistry.getRegistry方法接受一个普通的主机名，但您向它传递的是一个URL。有一个两个参数的形式，它接受一个主机名和一个端口号。

如果您希望使用URL来定位RMI服务，请使用java.rmi.Naming.lookup()。

Answer 2

"foo bar/Eo Nova“不是有效的主机名。

String szRemoteAdress = URL+"/"+WebConstants.SERVICE_NAME;

在这里，您要将"/"+WebConstants.SERVICE_NAME附加到主机名。

    Registry registry = LocateRegistry.getRegistry(szRemoteAdress);

在这里，您指定的不是主机名，而是刚刚构建的复合字符串。只需在此处使用主机名。

    EotGRemote stub = (EotGRemote) registry.lookup("EotGRemote");

这里你正在查找"EotGRemote“。WebConstants.SERVICE_NAME在其中扮演了什么角色？

这没有多大意义。