CFStream IOS Socket communication

Question

how can i clear an CFStream buffer? Everytime i read from socket there is still data from an old request, i mean complete response to an old request not just a fragment of it.

Am i missing something ?

This is a function i use to initialize the connection:

-(void)openSocketConnection:(UInt32)port: (NSString *)host
{
  NSString *hoststring  = [[NSString alloc] initWithString:host];
  CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault,(__bridge CFStringRef)hoststring ,
port,&_nnet_readStream,&_nnet_writeStream);

CFWriteStreamCanAcceptBytes(_nnet_writeStream);

CFWriteStreamSetProperty(_nnet_writeStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);

CFReadStreamSetProperty(_nnet_readStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);

    if(!CFWriteStreamOpen(_nnet_writeStream)) {
        NSLog(@"Error Opening Write Socket");
    }
    if(!CFReadStreamOpen(_nnet_readStream)) {
        NSLog(@"Error Opening Write Socket");
    }

}

This is a function i use to read data from socket:

BOOL done = NO;
NSMutableString* result = [NSMutableString string];
while (!done) 
{
        if (CFReadStreamHasBytesAvailable(_nnet_readStream)) 
        {
            UInt8 buf[1024];
            CFIndex bytesRead = CFReadStreamRead(_nnet_readStream, buf, 1024);
            if (bytesRead < 0) 
            {
                CFStreamError error = CFReadStreamGetError(_nnet_readStream);
                NSLog(@"%@",error);
            } else if (bytesRead == 0) 
            {
                if (CFReadStreamGetStatus(_nnet_readStream) == kCFStreamStatusAtEnd) 
                {
                    done = YES;
                }
            } else 
            {
                [result appendString:[[NSString alloc] initWithBytes:buf length:bytesRead encoding:NSUTF8StringEncoding]];
            }
        } else 
        {
            done = YES;
        }
}

score 0 · Answer 1 · answered Dec 24 '11 at 02:25

0

You seem to assume that when you get data from the host on the other end it will always be available all in one go.

I don't know what the underlying protocol is, but in general it's entirely possible that the remote end will try and send 1600 bytes and that you'll get 1500 bytes but then have to wait a few milliseconds (or even seconds) for the next 100 bytes. Meanwhile CFReadStreamHasBytesAvailable would return false and so your code would set your done flag even though you haven't read all the data the server sent.

answered Dec 24 '11 at 02:25

Frederick Cheung

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I used an example from apple doc reference to make this function. Do you have an example for a better solution? – Andreas Dec 24 '11 at 02:38
It entirely depends on what the other end of the connection is doing. Some protocols will tell you at the start how much data to expect, others have special markers that signify the end or other methods of telling you whether to expect more data. Others just close the connection when they are done. What ever the method you need to read the documentation/specifications in question to work out when you can consider yourself 'done' – Frederick Cheung Dec 24 '11 at 02:41
Ok well its entirely up to me since i program an server also. I will implement an end marker thank you for the hint. But the main problem remains. Everytime i read from socket there is still data from an old request, i mean complete response to an old request not just a fragment of it. – Andreas Dec 24 '11 at 02:51

CFStream IOS Socket communication

1 Answers1