java - Eclipse 和多播数据包的奇怪/无法解释的行为

Question

我的行为与描述非常相似here :

• 在 Mac Book Pro、Snow Leopard 上运行
• 使用多播套接字在本地主机上发送和接收数据包

我正在使用 Eclipse，当客户端/服务器从工作区启动时观察到以下行为:

• 如果无线接口(interface)(机场)已启动并正在运行，客户端不会接收任何数据包
• 如果界面关闭，一切都会按预期运行

但我不明白的是:

• 如果我创建一个 JAR 并在任何控制台中运行代码 -> 一切都好!只是 Eclipse 似乎不喜欢机场;-)
• 根据我连接的无线网络，上述行为可能会发生变化，即如果启用了机场(例如@ Uni)，它也可以工作

有人对此有什么想法吗？

干杯

下面是服务器/客户端的简单代码:

@Override
public void run() {
    String multicastAddress = "224.0.0.2";
    int multicastPort = 8000;
    MulticastSocket socket = null;
    try {
        try {
            InetAddress multicastGoup = InetAddress.getByName(multicastAddress);
            socket = new MulticastSocket(multicastPort);
            socket.joinGroup(multicastGoup);
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
        byte[] buffer = new byte[1024];

        while (true) {
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

            System.out.println("BEFORE RECEIVE: listening on " + multicastAddress + ":" + multicastPort);
            socket.receive(packet);
            System.out.println("PACKET RECEIVED");

            System.err.println("Client received: " + new String(packet.getData()));
        }

    } catch (UnknownHostException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        socket.close();
    }

}

服务器:

    public void run() {
    MulticastSocket socket = null;
    try {
        String multicastAddress = "224.0.0.2";
        int multicastPort = 8000;
        InetAddress multicastGoup = InetAddress.getByName(multicastAddress );
        socket = new MulticastSocket(multicastPort);
        socket.joinGroup(multicastGoup);

        byte[] data = new String("Teststring").getBytes();

        while (true) {
            socket.send(new DatagramPacket(data, data.length, multicastGoup, multicastPort));
            System.out.println("SERVER: Datagram sent");
            Thread.sleep(1000);
        }

    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        socket.close();
    }
}

Answer 1

来自Class MulticastSocket :

void  joinGroup(SocketAddress mcastaddr, NetworkInterface netIf)
          Joins the specified multicast group at the specified interface.

尝试使用特定的接口(interface)，这样您的 joinGroup 就不会落入默认值 - 这可能会因可用、开放的接口(interface)或 Eclipse 设置而异。

joinGroup

public void joinGroup(SocketAddress mcastaddr,
                      NetworkInterface netIf)
               throws IOException

  Joins the specified multicast group at the specified interface.

  If there is a security manager, this method first calls its
  checkMulticast method with the mcastaddr argument as its argument.

  Parameters:
    mcastaddr - is the multicast address to join
    netIf - specifies the local interface to receive
        multicast datagram packets,
      -- here is the catch
      or null to defer to the interface set by
        setInterface(InetAddress) or 
        setNetworkInterface(NetworkInterface)