GCDAsyncSocket didReadData only gets called once - gcdasyncsocket

Question

I am trying to set up a Java server talking to a iPhone client using GCDAsyncSocket. For some reason my client code on the iPhone is not reading back all of the data.
I see didReadData gets called the first time, but never again. Ideally, I need to mimic the functionality of the HTTP protocol where it sends a header and then the payload. The size of the payload would be in the header. But that wasn't working, so I simplified my code even further in hopes of finding the issue. Below is the code, and below that the output.
client:
- (BOOL) sendString:(NSString *) string
{
[asyncSocket writeData:[string dataUsingEncoding:NSUTF8StringEncoding]
withTimeout:-1 tag:TAG_PAYLOAD];
[asyncSocket readDataToLength:1 withTimeout:(-1) tag:TAG_HEADER];
}
- (void) socket:(GCDAsyncSocket *) sock didReadData:(NSData *)data
withTag:(long)tag
{
NSString *str = [[NSString alloc] initWithData:data
encoding:NSUTF8StringEncoding];
NSLog(#"Read data %# with tag: %ld", str, tag);
if(tag == TAG_HEADER)
{
//TODO - parse the header, get the fields
[sock readDataToLength:3 withTimeout:-1 tag:TAG_PAYLOAD];
//[sock readDataToData:[GCDAsyncSocket CRLFData] withTimeout:-1
tag:TAG_PAYLOAD];
}
else
{
NSLog(#"Payload... %#", str);
NSLog(#"Tag: %ld", tag);
}
}
Java server:
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
String clientCommand = in.readLine();
System.out.println("Client Says :" + clientCommand);
out.println("Andrew\r\nAUSTIN\r\n");
out.flush();
However, on the client, the only thing I get back is A. The exact output is:
Read data A with tag: 10
My question is:
How come the didReadData method is never called again? There should be more of "Andrew\r\nAustin" recv'd back on the client. But it just hangs. The readDataToData and readDataToLength both seem to never get the full string.
I noticed the CRLF defined in GCDAsyncSocket.h is not \r\n but instead the hex values. Does this matter? Thats why I tried the readDataToLength method but that still failed. But I would like to know if this matters cross-platform or not.
Thanks.

Answer 1

OK - so I figured it out after pulling out what little hair I have left.
What is happening is that I have client code above in a separate class outside of the view. Practically all of the examples I came across had the GCDAsyncSocket stuff handled inside the view. It works great in there! I really didn't want to do this because on each view I need to send/read data and didn't want to duplicate my work. By placing an NSLog() line in the dealloc method of this helper class, called SocketComm, I was able to see it was getting deallocated before it was firing. So I needed to change the way I was calling my helper class. I declare SocketComm* sockComm a strong property in the viewController.h file and allocated it in the viewDidLoad() method. This means that it stays in scope the whole time. Of course, this means I need to deallocate it manually and do some other housekeeping things.
I still am not sure if this is the best way to handle this situation either, as far as memory management goes. Because now I will have to alloc this on every viewDidLoad method. It seems like it should be simpler than this, but here we are. And I still don't know why it never read the data the first time (my only guess is that the GCDAsyncSocket library or the iphone software detected a dead thread when the parent that spawned it got deallocated and decided to terminate it - but this is only a guess as I have just started objective-c).
This would also explain why sometimes it would work and sometimes it wouldn't. It seemed like it was in a race condition. Not sure if the above code I originally posted resulted in a race condition exactly, but some things I would try would work, and then the next time fail. It never read more than the first time though, and only about half the time would it even read that. Sometimes it wouldn't even send the data out over the socket!
In summation (and for whoever else comes looking for an answer):
Always check your memory management. I had to place an NSLog in dealloc() of the SocketComm helper class to fully see what was happening, and as soon as I did that I knew what the culprit was.
If you get weird results where sometimes it works and sometimes it doesn't, check your memory management. For me, sometimes it would do the first read and sometimes it wouldn't. This lead me to believe the thread was getting terminated.
If I find a better way to do this I will come back and update this answer.
Memory management. Let me repeat: memory management.