SSDP on the iPhone - iphone

Question

I need to be able to send out a UDP message and also receive one in order to discover SSDP devices on the network from the iPhone.
I know that I need to send the packet to the multicast address and my HTTP request needs to look something like this:
M-SEARCH * HTTP/1.1
Host: 239.255.255.250:1900
Man: ssdp:discover
Mx: 3
ST: "urn:schemas-upnp-org:device:InternetGatewayDevice:1"
From reading the docs it appears that I can do all this with CFNetwork and despite reading (and re-reading the docs) I am struggling to get started. Can anyone recommend and tutorials or code snippets to get me over the initial learning hump?
I've got the CFNetwork programming guide:
http://developer.apple.com/mac/library/documentation/Networking/Conceptual/CFNetwork/CFNetwork.pdf
and Beej's Guide to Network programming Using Internet Sockets:
http://beej.us/guide/bgnet/
Thanks
Dave
P.S.
I am unable to use any of the 3rd party libraries and frameworks in this instance.

Answer 1

I have used AsyncUdpSocket successfully to run SSDP Discovery and find controllers. Here are my code snippets:
Initialize and setup the socket:
// AsyncUdpSocket *ssdpSock = [[AsyncUdpSocket alloc] initWithDelegate:self];
AsyncUdpSocket *ssdpSock = [[AsyncUdpSocket alloc] initIPv4];
[ssdpSock setDelegate:self];
Note the first line commented out. I found on the AsyncUdpSocket forums some issues with duplicates. I don't think I was facing them but I did it anyhow.
I added error checking, and it was useful because during my debugging I wasn't closing sockets and I started getting socket setup failures:
NSError *socketError = nil;
if (![ssdpSock bindToPort:1900 error:&socketError]) {
NSLog(#"Failed binding socket: %#", [socketError localizedDescription]);
return statusController;
}
if(![ssdpSock joinMulticastGroup:#"239.255.255.250" error:&socketError]){
NSLog(#"Failed joining multicast group: %#", [socketError localizedDescription]);
return statusController;
}
if (![ssdpSock enableBroadcast:TRUE error:&socketError]){
NSLog(#"Failed enabling broadcast: %#", [socketError localizedDescription]);
return statusController;
}
[ssdpSock sendData:[self.discoverControllerString dataUsingEncoding:NSUTF8StringEncoding]
toHost:#"239.255.255.250"
port:1900
withTimeout:2
tag:1];
Notice the changes I have made to the time out. And then finally did the receive setup, and closed the socket. Note the socket close. Since I am in my own class when I am running this - the code above did not work for me.
[ssdpSock receiveWithTimeout: 2 tag:1];
[NSTimer scheduledTimerWithTimeInterval: 5 target: self
selector:#selector(completeSearch:) userInfo: self repeats: NO];
[ssdpSock closeAfterSendingAndReceiving];
The most important change probably was returning "NO" if I did not find my controller. The first receive was incidentally the discovery message itself coming back. And when I read through the AsyncUdpSocket.h file carefully - returning "NO" when it is not a packet you are looking for helped.
Also note that I am using ARC in my code but I compiled the AsyncUdpSocket without ARC support.
-(void) completeSearch: (NSTimer *)t
{
NSLog(#"%s",__FUNCTION__);
//[ssdpSock close];
//ssdpSock = nil;
}
- (BOOL)onUdpSocket:(AsyncUdpSocket *)sock
didReceiveData:(NSData *)data
withTag:(long)tag
fromHost:(NSString *)host
port:(UInt16)port
{
NSLog(#"%s %ld %# %d",__FUNCTION__,tag,host,port);
NSString *aStr = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
NSLog(#"%#",aStr);
NSString *compareString = [aStr stringByPaddingToLength:[self.responseString length] withString:#"." startingAtIndex:0];
//NSLog(#"%#", compareString);
//NSLog(#"%#", self.responseString);
if ([compareString isEqualToString:self.responseString])
{
NSLog(#"String Compare, Controller Found!");
[self.controllerList addObject:aStr];
//NSData *controllerIP = [aStr dataUsingEncoding:NSUTF8StringEncoding];
[[NSNotificationCenter defaultCenter] postNotificationName:#"DiscoveredController" object:nil];
return YES;
}
return NO;
}

Answer 2

I have the following code for SSDP search in my app:
-(void)discoverDevices {
ssdpSock = [[AsyncUdpSocket alloc] initWithDelegate:self];
[ssdpSock enableBroadcast:TRUE error:nil];
NSString *str = #"M-SEARCH * HTTP/1.1\r\nHOST: 239.255.255.250:1900\r\nMan: \"ssdp:discover\"\r\nST: mydev\r\n\r\n";
[ssdpSock bindToPort:0 error:nil];
[ssdpSock joinMulticastGroup:#"239.255.255.250" error:nil];
[ssdpSock sendData:[str dataUsingEncoding:NSUTF8StringEncoding]
toHost: #"239.255.255.250" port: 1900 withTimeout:-1 tag:1];
[ssdpSock receiveWithTimeout: -1 tag:1];
[NSTimer scheduledTimerWithTimeInterval: 5 target: self
selector:#selector(completeSearch:) userInfo: self repeats: NO]; }
-(void) completeSearch: (NSTimer *)t {
NSLog(#"%s",__FUNCTION__);
[ssdpSock close];
ssdpSock = nil;}
- (BOOL)onUdpSocket:(AsyncUdpSocket *)sock didReceiveData:(NSData *)data withTag:(long)tag fromHost:(NSString *)host port:(UInt16)port{
NSLog(#"%s %d %# %d",__FUNCTION__,tag,host,port);
NSString *aStr = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
NSLog(#"%#",aStr);}
It uses the AsyncUdpSocket from CocoaAsyncSocket.

Answer 3

OK, finally done it. Found a class in the public domain (thanks Chris) called AsyncUdpSocket that lets you create a UDP socket which you can then turn on broadcasting and join the multicast address.
There is a nice sendData method, complete with adding to a run loop to prevent blocking.
Hope that helps.
Dave