网络应用程序可以在我的wifi上的计算机之间工作，但不能在其他计算机之间工作

Question

所以我刚开始学习套接字编程，我决定做一个非常基本的即时消息/聊天室。问题是，当我在我的wifi网络上的机器之间测试应用程序时，它运行得很好，但当我超出这个范围时，客户端无法连接。会不会是因为我使用了任意的端口号？

服务器：

public class MessengerServer {
private static ServerSocket serverSocket;
private static final int PORT=1234;

public static void main(String[] args) throws
        IOException {
    try{
        serverSocket=
                new ServerSocket(PORT);
    }
    catch(IOException e){
        System.out.println("Unable to open connection.");
        System.exit(1);
    }
    do{
        //wait for client
        Socket client= serverSocket.accept();

        System.out.println("New Client Accepted");

        //create a thread to handle communication 
        //with this client and pass the constructor
        //for this thread the relevant socket
        ClientHandler handler= //ClientHandler extends thread 
                new ClientHandler(client);
        handler.start();
    }while(true);
}

客户端(仅包含相关内容)：

public class InstantMessenger extends JFrame implements
    ActionListener{
    private static final int PORT= 1234; 
    private static InetAddress host;
    private static PrintWriter output;
    private static Socket link=null;
    private static byte[] ip= new byte[4]; //this is initialised with my IPAddress
                                   //which will not be shown.     


InstantMessenger(){

    try{
    host= InetAddress.getByAddress(ip);
    }
    catch(UnknownHostException uhEx){
        JOptionPane.showMessageDialog
                (this,"Unable to find host");
        System.exit(0);
    }
    try{
        link =new Socket(host,PORT);
        output=
            new PrintWriter(link.getOutputStream(),true);
        messageArea.append("\nConnected\n");
        }
    catch(IOException ioEx){
        messageArea.append("Unable to connect\n");
        }
}

客户端异常，StackTrace：

java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
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 instantmessenger.InstantMessenger.<init>(InstantMessenger.java:70)
at instantmessenger.InstantMessenger.main(InstantMessenger.java:132)

Answer 1

这可能是由服务器上的连接设置引起的。如果连接设置为在公网上，我认为默认情况下不允许接受来自其他网络的连接。此外，请检查是否有任何防火墙设置会阻止来自其他子网的传入连接。