How to use NSInputStream and NSOutputStream - ios

Question

I am trying to create a simple multiplayer turn-based game between iPhones. Right now all I want to do is pass in some string to my method, and have the method send the string through the NSOutputStream. I think I have properly connected my NSNetServices using NSNetServiceBrowser. Once they connect, my NSNetServiceDelegate has netService:didAcceptConnectionWithInputStream:outputStream: called, which should give me my i/o NSStream pair. My method looks like this:
-(void)netService:(NSNetService *)sender didAcceptConnectionWithInputStream:(NSInputStream *)inputStream outputStream:(NSOutputStream *)outputStream{
[self.myNet getInputStream:&inputStream outputStream:&outputStream];
self.inStream = inputStream;
self.outStream = outputStream;
[self.inStream setDelegate:self];
[self.inStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[self.inStream open];
}
I think I have correctly set up NSInputStream. I also have a delegate for NSStream which is implementing stream:handleEvent:
It looks like this:
-(void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode{
NSInputStream *inStream = (NSInputStream *)aStream;
BOOL shouldClose = NO;
switch(eventCode) {
case NSStreamEventEndEncountered:
shouldClose = YES;
// If all data hasn't been read, fall through to the "has bytes" event
if(![inStream hasBytesAvailable]) break;
case NSStreamEventHasBytesAvailable: ; // We need a semicolon here before we can declare local variables
uint8_t *buffer;
NSUInteger length;
BOOL freeBuffer = NO;
// The stream has data. Try to get its internal buffer instead of creating one
if(![inStream getBuffer:&buffer length:&length]) {
// The stream couldn't provide its internal buffer. We have to make one ourselves
buffer = malloc(BUFFER_LEN * sizeof(uint8_t));
freeBuffer = YES;
NSInteger result = [inStream read:buffer maxLength:BUFFER_LEN];
if(result < 0) {
// error copying to buffer
break;
}
length = result;
}
// length bytes of data in buffer
if(freeBuffer) free(buffer);
break;
case NSStreamEventErrorOccurred:
// some other error
shouldClose = YES;
break;
case NSStreamEventHasSpaceAvailable:
break;
case NSStreamEventNone:
break;
case NSStreamEventOpenCompleted:
break;
}
if(shouldClose){
[inStream close];
}
}
I took that code from: this page. In that code, aStream should be self.inStream. I have looked at pages describing what to do for NSOutputStream, but none of them seem to be geared at a beginner like me. I have a few questions. Firstly, how do I set up a method that I pass the data in (NSData or maybe an NSString) and it sends it out through self.outStream. I would prefer an answer that explains the code, rather than just giving it to me. Secondly, should I open both of my streams in netService:didAcceptConnectionWithInputStream:outputStream:, and should I also scheduleInRunLoop the NSOutputStreamself.outStream`. Finally, am I doing everything wrong?
Thanks for your answers. Also this is my first question, so any constructive criticism is welcomed.

Answer 1

To write to output stream, check stream has space available and write data using
- (NSInteger)write:(const uint8_t *)buffer maxLength:(NSUInteger)length
So, code may be like following.
if ( self.outStream.hasSpaceAvailable ) [ self.outStream write:... maxLength: ];
If output stream doesn't have space available, later
-(void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
method of the delegate of output stream would be called with eventCode = NSStreamEventHasSpaceAvailable.
You should open output stream and schedule it in netService:didAcceptConnectionWithInputStream:outputStream or when you receive NSStreamEventOpenCompleted of input stream. Both are OK.
If you don't want writing block thread, you need to prepare queue.
So code is like following
NSMutableData* uQueue;
NSInputStream* uIStream;
NSOutputStream* uOStream;
:
:
:
uIStream.delegate = self;
uOStream.delegate = self;
[ uIStream scheduleInRunLoop:NSRunLoop.currentRunLoop forMode:NSDefaultRunLoopMode ];
[ uOStream scheduleInRunLoop:NSRunLoop.currentRunLoop forMode:NSDefaultRunLoopMode ];
[ uIStream open ];
[ uOStream open ];
uQueue = NSMutableData.data;
:
:
:
- (void)
Send
{ if ( uQueue.length )
{ NSInteger wLength = [ uOStream write:(const uint8_t*)uQueue.bytes maxLength:uQueue.length ];
if ( wLength > 0 ) [ uQueue replaceBytesInRange:NSMakeRange( 0, wLength ) withBytes:NULL length:0 ];
}
}
- (void)
Write:(NSData*)p
{ [ uQueue appendData:p ];
if ( uOStream.hasSpaceAvailable ) [ self Send ];
}
- (void)
stream:(NSStream*)pS
handleEvent:(NSStreamEvent)p
{ switch( p )
{
:
:
:
case NSStreamEventHasSpaceAvailable:
[ self Send ];
break;
}
}