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SSDP Service using Java/OSGi [Part 3, ROM]

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In the last part I talked about how I implemented the SSDP code on the IOS app, to make my device discoverable – it has to be running the “SSDP Advertiser” – or a server that is listening to discovery messages.

The SSDP service runs as a thread when the OSGi bundle is installed and started – “AdvertiseServiceSSDP()”. [The call before that – SocksServer is the class that implements the network interface between the IOS app & the Plug Computer as explained in the project overview.

public void start(BundleContext bc) throws Exception {
    this.bc = bc;
    nServer = new SocksServer(bc);
    advtROMService = new AdvertiseServiceSSDP(bc);
  }

Here is the SSDP code:

public void run() {
String msg = "LISTEN-FOR=THIS MESSAGE";
String chkResponse = "RESPOND-WITH-THIS-MESSAGE";
try {
int port = 1900;
InetAddress listenSSDP = InetAddress.getByName("239.255.255.250");
MulticastSocket ms = new MulticastSocket(port);  // Create socket
ms.joinGroup(listenSSDP);
System.out.println("\n Rcvr started, Ready to Receive... \n");
boolean match = false;
do {
byte[] response = new byte[256];
DatagramPacket rspPkt = new DatagramPacket(response, response.length);
ms.receive(rspPkt);
//System.out.println("\n Done Receiving!\n");
String getResponse;
getResponse = new String(rspPkt.getData());
match = getResponse.regionMatches(0, msg, 0, msg.length());
if (match)
{
System.out.println("Controller found\n");
// Send Response
InetAddress IPAddress = rspPkt.getAddress();
byte[] sendData = new byte[1024];
String sendResponse = chkResponse;
sendResponse += IPAddress.getHostName();
sendResponse += "/:portAddr";
System.out.println(sendResponse);
sendData = sendResponse.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 1900);
ms.send(sendPacket);
System.out.println("Response Sent");
match = false;
}
} while(match==false);
} catch(Exception ignore) {
System.out.println(ignore.getMessage());
}
}

The above code when running on the Plug Computer(s) allows the IOS app to discover them. Of course the beauty is that this will work for all devices that support OSGi/JVM and have multicast networking support.

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Written by Ashu Joshi

May 4, 2012 at 2:48 pm

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