Android SSDP服务发现

Question

我正在实现一个java程序，该程序使用SSDP发现扫描我拥有的一些智能设备。我使用的代码只检测到10个连接到本地网络的设备中的2个。我不明白原因是什么。

我的问题是，为什么我无法获得本地网络中的所有设备。

这是我正在使用的代码

static final String HOST = "Host:" + SSDP.ADDRESS + ":" + SSDP.PORT;
static final String MAN = "Man: "ssdp:discover"";
 static final String NEWLINE = "rn";
int mMX = 10;    /* seconds to delay response */
String mST;     /* Search target */
public SSDPSearchMsg(String ST) {
    mST = ST;
}
public int getmMX() {
    return mMX;
}
public void setmMX(int mMX) {
    this.mMX = mMX;
}
public String getmST() {
    return mST;
}
public void setmST(String mST) {
    this.mST = mST;
}
@Override
public String toString() {
    StringBuilder content = new StringBuilder();
    content.append(SSDP.SL_MSEARCH).append(NEWLINE);
    content.append(HOST).append(NEWLINE);
    content.append(MAN).append(NEWLINE);
    content.append(mST).append(NEWLINE);
    content.append("MX:" + mMX).append(NEWLINE);
    content.append(NEWLINE);
    return content.toString();
}

以下是几个常数

 /* New line definition */
public static final String NEWLINE = "rn";
public static final String ADDRESS = "239.255.255.250";
public static final int PORT = 1900;
/* Definitions of start line */
public static final String SL_NOTIFY = "NOTIFY * HTTP/1.1";
public static final String SL_MSEARCH = "M-SEARCH * HTTP/1.1";
public static final String SL_OK = "HTTP/1.1 200 OK";
/* Definitions of search targets */
public static final String ST_RootDevice = "ST: upnp:rootdevice";
public static final String ST_ContentDirectory = "ST: urn:schemas-upnp-org:service:ContentDirectory:1";
public static final String ST_ALL="ST: ssdp:all";
public static final String ST_Media="ST:urn:schemas-upnp-org:device:MediaRenderer:1";

/* Definitions of notification sub type */
public static final String NTS_ALIVE = "NTS:ssdp:alive";
public static final String NTS_BYE = "NTS:ssdp:byebye";
public static final String NTS_UPDATE = "NTS:ssdp:update";

主类

public class SSDPSocket {
SocketAddress mSSDPMulticastGroup;
MulticastSocket mSSDPSocket;
public SSDPSocket() throws IOException {
    InetAddress localInAddress = InetAddress.getLocalHost();
    System.out.println("Local address: " + localInAddress.getHostAddress());
    mSSDPMulticastGroup = new InetSocketAddress(SSDP.ADDRESS, SSDP.PORT);
    mSSDPSocket = new MulticastSocket(new InetSocketAddress(localInAddress,
            0));
    NetworkInterface netIf = NetworkInterface
            .getByInetAddress(localInAddress);
    mSSDPSocket.joinGroup(mSSDPMulticastGroup, netIf);
}
/* Used to send SSDP packet */
public void send(String data) throws IOException {
    DatagramPacket dp = new DatagramPacket(data.getBytes(), data.length(),
            mSSDPMulticastGroup);
    mSSDPSocket.send(dp);
}
/* Used to receive SSDP packet */
public DatagramPacket receive() throws IOException {
    byte[] buf = new byte[1024];
    DatagramPacket dp = new DatagramPacket(buf, buf.length);
    mSSDPSocket.receive(dp);
    return dp;
}
public void close() {
    if (mSSDPSocket != null) {
        mSSDPSocket.close();
    }
}
/* For test purpose */
public static void main(String[] args) {
    SSDPSearchMsg search = new SSDPSearchMsg(SSDP.ST_Media);
    System.out.println(search.toString());
    SSDPSocket sock;
    try {
        sock = new SSDPSocket();
        sock.send(search.toString());
        while (true) {
            DatagramPacket dp = sock.receive();
            String c = new String(dp.getData());
            System.out.println(c);
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
    }
}

有人能为这个问题提出一个解决方案吗？

Answer 1

我刚刚开发了一个SSDP Java客户端，并仔细研究了规范。

您缺少一个"MX"标头。如果没有设置头MX，则SSDP服务"应该"不会响应您的请求。因此，请尝试添加一个"MX:1"标头，并查看它的去向。

Schneider数据库对这个问题有很好的帮助。

此外，如果您仍在尝试使用ssdp客户端，您可以查看它。