problem with the writing TCP socket in objective c (error message)

i'm have problem with the writing TCP socket in objective c. i'm having the following error when i then to write a string to my server. some help please?

• error writing to stream <__NSCFOutputStream: 0x102009f0>: Error Domain=NSPOSIXErrorDomain Code=9 "

the following are my code. Thanks inn advance

- (void)setup {

    host = // some adderss;
    port = // port;

    NSURL *url = [NSURL URLWithString:host];

    NSLog(@"Setting up connection to %@ : %i", [url absoluteString], port);

    CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, (CFStringRef)[url host], port, &readStream, &writeStream);

    if(!CFWriteStreamOpen(writeStream)) {
        NSLog(@"Error, writeStream not open");

        return;
     }  


    [self open]; 

    NSLog(@"Status of outputStream: %i", [outputStream streamStatus]);

    return;
}

- (void)open {
    NSLog(@"Opening streams.");
    CFReadStreamSetProperty(readStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);
    CFWriteStreamSetProperty(writeStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);

    inputStream = (NSInputStream *)readStream;
    outputStream = (NSOutputStream *)writeStream;

    [inputStream retain];
    [outputStream retain];

    [inputStream setDelegate:self];
    [outputStream setDelegate:self];

    [inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

    [inputStream open];
    [outputStream open];
}

- (void)close {
    NSLog(@"Closing streams.");

    [inputStream close];
    [outputStream close];

    [inputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [outputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

    [inputStream setDelegate:nil];
    [outputStream setDelegate:nil];

    [inputStream release];
    [outputStream release];

    inputStream = nil;
    outputStream = nil;
}

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)event {
    NSLog(@"Stream triggered.");
    NSLog(@"dddd%i", event);

    switch(event) {
        case NSStreamEventHasSpaceAvailable: {
            if(stream == outputStream) {
                NSLog(@"outputStream is ready.");


                NSString *s =@"12";

                [self writeOut:s];
            }
            break;
        }
        case NSStreamEventHasBytesAvailable: {
            if(stream == inputStream) {
                NSLog(@"inputStream is ready."); 

                uint8_t buf[1024];
                unsigned int len = 0;

                len = [inputStream read:buf maxLength:1024];

                if(len > 0) {
                    NSMutableData* data=[[NSMutableData alloc] initWithLength:0];

                    [data app开发者_如何学JAVAendBytes: (const void *)buf length:len];

                    NSString *s = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];

                    [self readIn:s];

                    [data release];
                }
            } 
            break;
        }
        default: {
            NSLog(@"Stream is sending an Event: %i", event);

            break;
        }
    }
}

- (void)readIn:(NSString *)s {



    NSLog(@"Reading in the following:");
    NSLog(@"%@", s);
}

- (void)writeOut:(NSString *)s {
    uint8_t *buf = (uint8_t *)[s UTF8String];

    NSInteger nwritten=[outputStream write:buf maxLength:strlen((char *)buf)];
    if (-1 == nwritten) {
        NSLog(@"Error writing to stream %@: %@", outputStream, [outputStream streamError]);
    } else {
        NSLog(@"Wrote %ld bytes to stream %@.", (long)nwritten, outputStream);
    }
    NSLog(@"Writing out the following:");
    NSLog(@"%@", s);

Your code actually is all right and works (I tested it). The error you’re getting has error code 9 in the POSIX domain, which is EBADF (you can look up the posix error codes in /usr/include/sys/errno.h). EBADF means you are trying to write to an invalid file descriptor - you didn’t really open the socket.

My guess is that you didn’t show the error. What is the actual value of the string host? If that’s just the host name or IP address this can’t work, since you are constructing an URL from it and taking the host part of this URL to connect to.

I had this same problem and 2 things solved it for me:

1) waiting until the socket was fully open: I was testing the code out using a Foundation command line tool, which would exit before the socket had a chance to fully open. This was fixed with a simple loop like this:

int i = 0;
while( i++ < 20 )
{
    NSLog( @" has space %i, %i", [socket hasSpace], i );
    if( ![socket hasSpace] )
        continue;
    [socket writeOut:@"Hello world"];
    break;
}

hasSpace was simply returning [outputStream hasSpaceAvailable]

2) I was trying to connect to a server using the host NSString* "localhost", when it should have been "http://localhost"