Question

I’m trying to send a file on FTP server in my iPhone application.
Everything seems to be okay in WiFi and GSM:EDGE network, but in 3G network an error appears (not always, but very often):

Error Domain=NSPOSIXErrorDomain
Code=12 “The operation couldn’t be
completed. Cannot allocate memory”

Below the code where the error appears:

- (void)stream:(NSStream*)aStream handleEvent:(NSStreamEvent)eventCode {

    switch( eventCode ) {
        case NSStreamEventHasSpaceAvailable: {
            if( _readDataOffset == _readDataLimit ) {
                NSInteger readDataLen = [_readStream read:[_readData mutableBytes] maxLength:kReadDataLength];
                NSLog(@"readDataLen is %d",readDataLen);
                if( -1 == readDataLen ) {
                    _error = [[_readStream streamError] retain];
                    _keepRunning = NO;
                } else if( 0 == readDataLen ) {
                    _keepRunning = NO;
                } else {
                    _readDataOffset = 0;
                    _readDataLimit = readDataLen;
                }
            }

            if( _readDataOffset != _readDataLimit ) {
                NSOutputStream* writeStream = (NSOutputStream*)aStream;

                uint8_t *buffer = (void *)[_readData bytes];

          // vvvv and here  the value of writtenDataLen is often -1 (but only on 3G network)
                NSInteger writtenDataLen = [writeStream write:&buffer[_readDataOffset] maxLength:_readDataLimit - _readDataOffset]; 


                if( writtenDataLen > 0 ) {
                    _readDataOffset += writtenDataLen;
                    _writtenDataLen += writtenDataLen;
                    [self ftpPutDidWriteInternal];
                } else if( -1 == writtenDataLen ) {
                    _error = [[writeStream streamError] retain];
                    _keepRunning = NO;
                }
            }

        } break;
        case NSStreamEventErrorOccurred: {
            _error = [aStream.streamError retain];
            _keepRunning = NO;
        } break;
    }    
}

What can be important, the whole sending is done in separate thread which has it’s own NSAutoreleasePool.
Is there anyone who got the issue? Any suggestion? I would be appreciate.

UPDATE:
I’ve just checked that popular iPhone application “FTP On The Go” has got the same (?) issue during sending a file in 3G network! There is no error handled, but the transfer stops.

UPDATE 2:
I can’t believe it, but it’s true: SimpleFTPSample from Apple is also affected with the issue.

Answer 1

And here it is – the solution (or rather workaround):

you should set property of writeStream to false, to switch off default persistant connection

CFWriteStreamSetProperty( (CFWriteStreamRef)writeStreamRef, kCFStreamPropertyFTPAttemptPersistentConnection, kCFBooleanFalse ) ;