SSDP协议的Android实现以及使用

大家好，又见面了，我是全栈君，祝每个程序员都可以多学几门语言。

前面一篇博客里面已经介绍过SSDP协议原理，本篇博客将实现实现Android上的SSDP协议。

关键技术分析：1、发送广播；须要发送送广播，所以须要使用MulticastSocket、SocketAddress、InetAddress，须要掌握。

2、SSDP数据报格式；标准的SSDP Server解析的时候对于分段的字段选用的特征码是”\r\n”，须要特别注意。

3、訪问权限；须要互联网，要在Mainfest中加入�联网的相关权限。

下面是我的源代码：

1、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;
public static final String SL_MSEARCH = “M-SEARCH * HTTP/1.1”;
public static final String SL_OK = “HTTP/1.1 200 OK”;
public static final String ST_Product = “ST:urn:schemas-upnp-org:device:Server:1”;
public static final String Found = “ST=urn:schemas-upnp-org:device:”;
public static final String Root = “ST:urn:schemas-upnp-org:device:DZBA_HomeDP:1”;
}

2、SSDPSearchMsg .java

public class SSDPSearchMsg {
static final String HOST = “Host:” + SSDP.ADDRESS + “:” + SSDP.PORT;
static final String MAN = “Man:\”ssdp:discover\””;
static final String NEWLINE = “\r\n”;
int mMX = 5; /* 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(“MX:” + mMX).append(NEWLINE);
content.append(mST).append(NEWLINE);
content.append(NEWLINE);
return content.toString();
}
}

3、SSDPSocket .java

public class SSDPSocket {

SocketAddress mSSDPMulticastGroup;
MulticastSocket mSSDPSocket;
InetAddress broadcastAddress;

public SSDPSocket() throws IOException {
mSSDPSocket = new MulticastSocket(58000); // 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();
}
}
}

4、SSDP .java

public class SSDP {
/* 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;
public static final String ST = “ST”;
public static final String LOCATION = “LOCATION”;
public static final String NT = “NT”;
public static final String NTS = “NTS”;
/* 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”;

@SuppressWarnings(“resource”)
public static String parseHeaderValue(String content, String headerName) {
Scanner s = new Scanner(content);
s.nextLine(); // Skip the start line
while (s.hasNextLine()) {
String line = s.nextLine();
int index = line.indexOf(‘:’);
String header = line.substring(0, index);
if (headerName.equalsIgnoreCase(header.trim())) {
return line.substring(index + 1).trim();
}
}
return null;
}

public static String parseHeaderValue(DatagramPacket dp, String headerName) {
return parseHeaderValue(new String(dp.getData()), headerName);
}

@SuppressWarnings(“resource”)
public static String parseStartLine(String content) {
Scanner s = new Scanner(content);
return s.nextLine();
}

public static String parseStartLine(DatagramPacket dp) {
return parseStartLine(new String(dp.getData()));
}
}

5、MainActivity .java

public class MainActivity extends Activity implements OnClickListener {
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.Root);
SSDPSocket sock = null;
try {
sock = new SSDPSocket();
for (int i = 0; i < 2; i++) {
// sock.send(searchContentDirectory.toString());
// sock.send(searchAVTransport.toString());
sock.send(searchProduct.toString());
// String s = “M-SEARCH * HTTP/1.1 \n HOST= 239.255.255.250:1900 \n MAN= \”ssdp:discover\” \n MX: 3 \n ST= upnp:rootdevice”;
// sock.send(s);
Log.i(“————-“, “发送的数据为：\n” + 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()).trim();
String ip = new String(dp.getAddress().toString()).trim();
Log.i(“————“, “接收到的数据为：\n” + c + “數據來源IP：” + ip);
}
} catch (IOException e) {
Log.e(“M-SEARCH”, e.getMessage());
}
}
}

界面xml非常easy，仅仅有一个button

Mainfest.xml:

<?xml version=”1.0″ encoding=”utf-8″?>
<manifest xmlns:android=”http://schemas.android.com/apk/res/android”
package=”com.example.ssdp”
android:versionCode=”1″
android:versionName=”1.0″ >

<uses-sdk
android:minSdkVersion=”8″
android:targetSdkVersion=”18″ />

<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” />