在 Java 中忽略您自己的 UDP 广播

2022-01-22 00:00:00 network-programming udp java

在我的程序中，我发送 UDP 广播并对它们做出反应.我需要一种方法来忽略 我 发出的 UDP 广播，但对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.

我确实尝试过使用:if (NetworkInterface.getByInetAddress(packet.getAddress()) != null)但这在某些情况下会产生 IOExceptions(java.net.SocketException: no network interface is bound to such an IP address)

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)

有人有什么想法吗?

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

Also: getInetAddress() on my socket throws a NullPointerException

推荐答案

我觉得javadoc和NetworkInterface getByInetAddress()的实际实现有点出入.javadoc 似乎建议 getByInetAddress 如果未找到匹配项将返回 null，但实现要么返回匹配项，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:一个 NetworkInterface 或 如果没有具有指定 IP 地址的网络接口，则返回 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");
  }

我建议要么捕获异常并将其视为来自第 3 方的答案，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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