在Java中忽略您自己的UDP广播 [英] Ignoring your own UDP broadcasts in Java

问题描述

在我的程序中，我发送UDP广播并对它们作出反应。我需要一种方法来忽略我发送的UDP广播，但对那些不是来自我的机器的广播做出反应。

In my program I'm sending out UDP broadcasts and reacting to them. I need a way to ignore the UDP broadcasts that I send out, but react to ones that aren't from my machine.

我做了尝试使用：
if（NetworkInterface.getByInetAddress（packet.getAddress（））！= null）
但在某些情况下这会生成IOExceptions（java。 net.SocketException：没有网络接口绑定到这样的IP地址）

I did try using: if (NetworkInterface.getByInetAddress(packet.getAddress()) != null) but this generated IOExceptions in some cases (java.net.SocketException: no network interface is bound to such an IP address)

任何想法？

：我的套接字上的
getInetAddress（）抛出一个NullPointerException

Also: getInetAddress() on my socket throws a NullPointerException

推荐答案

我认为javadoc与之间存在一点差异实际实现 NetworkInterface getByInetAddress（）。 javadoc似乎暗示如果没有找到匹配，getByInetAddress将返回null，但实现要么返回匹配，要么抛出SocketException。

I think there's a little discrepancy between the javadoc and the actual implementation of NetworkInterface getByInetAddress(). The javadoc seems to suggest that getByInetAddress would return null if no match was found, yet the implementation either returns a match, either throws a SocketException.

public static NetworkInterface getByInetAddress(InetAddress addr)
                                               throws SocketException

返回：如果没有指定IP地址的网络接口，则返回NetworkInterface或 null。

Returns: A NetworkInterface or null if there is no network interface with the specified IP address.

  public static NetworkInterface getByInetAddress (InetAddress addr)
    throws SocketException
  {
    if (networkInterfaces == null)
      networkInterfaces = getRealNetworkInterfaces ();

    for (Enumeration interfaces = networkInterfaces.elements ();
         interfaces.hasMoreElements (); )
      {
        NetworkInterface tmp = (NetworkInterface) interfaces.nextElement ();

        for (Enumeration addresses = tmp.inetAddresses.elements ();
             addresses.hasMoreElements (); )
          {
            if (addr.equals ((InetAddress) addresses.nextElement ()))
              return tmp;
          }
      }

    throw new SocketException (
      "no network interface is bound to such an IP address");
  }

我建议要么抓住异常并将其视为第3个答案派对，要么使用 getNetworkInterfaces（）方法重新实现它。

I suggest to either catch the exception and treat it as an answer from a 3rd party, either re-implement it using the getNetworkInterfaces() method.

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