我正在尝试在我的android应用程序中实现一个非常简单的SSDP功能。

我的应用程序向广播地址发送了一些UDP数据包，其中包含相关的M-SEARCH消息，没有任何问题。问题是，我应该从其他运行UPNP服务器的设备得到正确的响应。由于某种原因，我只收到了从我的android设备上发送回来的完全相同的数据包。

Mainactivity.java

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        WifiManager wm = (WifiManager)getSystemService(Context.WIFI_SERVICE);
        WifiManager.MulticastLock multicastLock = wm.createMulticastLock("multicastLock"); 
        multicastLock.setReferenceCounted(true);
        multicastLock.acquire();

        setContentView(R.layout.activity_main);

        ((Button)this.findViewById(R.id.btnSendSSDPSearch)).setOnClickListener(this);
    }

@Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.btnSendSSDPSearch:
            new Thread(new Runnable() {

                @Override
                public void run() {
                    SendMSearchMessage();
                }
            }).start();

        default:
            break;
        }
    }

private void SendMSearchMessage() {

                SSDPSearchMsg searchContentDirectory = new SSDPSearchMsg(SSDPConstants.ST_ContentDirectory);
    SSDPSearchMsg searchAVTransport = new SSDPSearchMsg(SSDPConstants.ST_AVTransport);
    SSDPSearchMsg searchProduct = new SSDPSearchMsg(SSDPConstants.ST_Product);

    SSDPSocket sock;
    try {
        sock = new SSDPSocket();
        for (int i = 0; i < 2; i++) { 
            sock.send(searchContentDirectory.toString());
            sock.send(searchAVTransport.toString());
            sock.send(searchProduct.toString());
        }

      while (true) {
            DatagramPacket dp = sock.receive(); //Here, I only receive the same packets I initially sent above
            String c = new String(dp.getData());
            System.out.println(c); 
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        Log.e("M-SEARCH", e.getMessage());

    }

SSDPSocket.java，其中UDP数据包传输实际完成

public class SSDPSocket {
    SocketAddress mSSDPMulticastGroup;
    MulticastSocket mSSDPSocket;
    InetAddress broadcastAddress;

    public SSDPSocket() throws IOException {
        mSSDPSocket = new MulticastSocket(55325); //Bind some random port for receiving datagram
        broadcastAddress  = InetAddress.getByName(SSDPConstants.ADDRESS);
        mSSDPSocket.joinGroup(broadcastAddress);
    }

    /* Used to send SSDP packet */
    public void send(String data) throws IOException {
        DatagramPacket dp = new DatagramPacket(data.getBytes(), data.length(),
                broadcastAddress,SSDPConstants.PORT);

        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();
        }
    }
}

用于构造SSDP广播字符串的ssdpsearchmsg.java（可能与我遇到的问题无关，但以防万一）

public class SSDPSearchMsg {
    static final String HOST = "Host:" + SSDP.ADDRESS + ":" + SSDP.PORT;
    static final String MAN = "Man:ssdp:discover";
    static final String NEWLINE = System.getProperty("line.separator");

    int mMX = 3;    /* 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();
    }
}

SSDPConstants.java

public class SSDPConstants {
    /* New line definition */
    public static final String NEWLINE = "\r\n";

    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: rootdevice";
    public static final String ST_ContentDirectory = "St: urn:schemas-upnp-org:service:ContentDirectory:1";
    public static final String ST_AVTransport = "St: urn:schemas-upnp-org:service:AVTransport:1";
    public static final String ST_Product = "St: urn:av-openhome-org:service:Product: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";
}

我还确保清单包括相关权限:

 <uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

我是在实际设备上测试这个应用程序，而不是在模拟器上。

如有任何协助，将不胜感激。

评论时编辑:

组播本身应该不会出现问题。我下载了一个名为BubbleUPNP的应用程序来测试SSDP的功能。果不其然，wireshark在SSDP协议中恰当地捕获了从电话发送到广播地址的所有消息:

M-SEARCH * HTTP/1.1

Man: "ssdp:discover"

Mx: 3

Host: 239.255.255.250:1900

St: urn:schemas-upnp-org:service:AVTransport:1

和响应

HTTP/1.1 200 OK

ST:urn:schemas-upnp-org:service:ContentDirectory:1

USN:uuid:d5829e90-73ce-4213-9ad1-4e75dbdd0232::urn:schemas-upnp-org:service:ContentDirectory:1

Location:http://10.175.95.4:2869/upnphost/udhisapi.dll?content=uuid:d5829e90-73ce-4213-9ad1-4e75dbdd0232

OPT:"http://schemas.upnp.org/upnp/1/0/"; ns=01

01-NLS:05f3dd08b4b4b5aafa1fe983fa447f49

Cache-Control:max-age=900

Server:Microsoft-Windows-NT/5.1 UPnP/1.0 UPnP-Device-Host/1.0

所以，毫无疑问，这是一个实施问题。装置没有问题。