Question

我在同一个子网上有一个Android客户端和普通Java服务器，我正在从客户端向服务器发送UDP广播数据包。对于一些路由器（Netgear，Cisco），服务器很乐意接收数据包，但是对于我的Asus路由器，而服务器 machine 接收数据包，服务器 DatagramSocket 不会。

NB在所有情况下，Wireshark显示数据包已到达服务器计算机。但是当使用华硕路由器时，DatagramSocket似乎并没有看到它们。为了简单起见，服务器只与路由器建立了以太网连接。

代码非常标准。

客户端：

DatagramSocket socket = null;
try {
    socket = new DatagramSocket();
    socket.setSoTimeout(500); // 500 millis

    while (isRunning()) {
        final InetAddress broadcastAddress = getSubnetBroadcastAddress();
        final DatagramPacket outboundPacket = new DatagramPacket(REQUEST_MESSAGE, REQUEST_MESSAGE.length, broadcastAddress, broadcastPort);
        socket.send(outboundPacket);
    }

} catch (IOException e) {
    Log.i(TAG, "Beacon failed", e);
} finally {
    if (socket != null) {
        socket.close();
    }
}

private InetAddress getSubnetBroadcastAddress() throws IOException {
    final WifiManager wifi = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
    final DhcpInfo dhcp = wifi.getDhcpInfo();
    if (dhcp == null) {
        // No successful DHCP request. Go with best effort.
        Log.d(TAG, "#getBroadcastAddress - No DHCP info so using generic broadcast address");
        return InetAddress.getByName("255.255.255.255");
    }

    final int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
    final byte[] quads = new byte[4];
    for (int k = 0; k < 4; k++) {
        quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
    }
    return InetAddress.getByAddress(quads);
}

服务器：

    DatagramSocket socket = null;
    try {
        socket = new DatagramSocket(broadcastPort);
        socket.setSoTimeout(LISTENING_TIMEOUT);
        socket.setBroadcast(true);
        while (keepRunning) {
            try {
                final byte[] buffer = new byte[1024];
                final DatagramPacket receivedPacket = new DatagramPacket(buffer, buffer.length);
                socket.receive(receivedPacket);
                log.debug("Received packet : " + receivedPacket.toString());
            } catch (SocketTimeoutException e) {
                log.debug("#run BeaconRunnable socket timed out");
            }
        }
    } catch (IOException e) {
        log.warn("Error while receiving message", e);
        if (socket != null) {
            socket.close();
        }
    }

导致DatagramSocket无法使用华硕路由器查看UDP广播数据包的原因是什么？

Answer 1

对于那些跟随...

上面的代码没有任何问题。路由器配置没有任何问题。

Windows防火墙中添加了一条规则，阻止来自公共连接的传入UDP，并且出于某种原因，Asus路由器被视为公共连接。

禁用该规则可以让一切正常。

Java DatagramSocket没有从某些路由器接收UDP广播

1 个答案: