java - How to determine an incoming connection is from local machine

Question

I have a SocketServer accepting incoming connections. For security reasons I should only allow local connections (connections from the machine on which server is running).

How can I determine if an incoming connection is from another machine? Is the following code safe for this?

Socket socket = someServerSocket.accept();
String remoteAddress = socket .getInetAddress().getHostAddress();
if (!fromThisMachine(remoteAddress)) {
    // Not from this machine.
}

while fromThisMachine() method is like this:

public boolean fromThisMachine(String remoteAddress) {
    try {
        Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
        while (interfaces.hasMoreElements()) {
            NetworkInterface networkInterface = interfaces.nextElement();
            Enumeration<InetAddress> addresses = networkInterface.getInetAddresses();
            while (addresses.hasMoreElements()) {
                InetAddress inetAddress = addresses.nextElement();
                String hostName = inetAddress.getHostName();
                String hostAddr = inetAddress.getHostAddress();
                if (hostName.equals(remoteAddress) || hostAddr.equals(remoteAddress)) {
                    return true;
                }
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
    log("Unauthorized request to server from: " + remoteAddress);
    return false;
}

Thanks, Mohsen

Answer 1

InetAddress.getByName( null ) always returns the loopback address. See the javadoc

    int port = .....
    SocketAddress socketAddress =
        new InetSocketAddress( InetAddress.getByName( null ), port);
    ServerSocket serverSocket = new ServerSocket();
    serverSocket.bind(socketAddress);
    serverSocket.accept();