Socket issues between iOS and .NET?

Question

I have a .NET desktop program running as a server and I'm trying to implement a port of my client program in iOS, but I'm getting some odd behavior from NSSocket. Here's the relevant code from the server.

public NetworkListener()
{
    _Stream = new MemoryStream();
    _tcpServer = new TcpListener(System.Net.IPAddress.Any, 8086);
    _endPoints = new List<EndPoint>();
}

public void BeginListening()
{
    _tcpServer.Start();
    _workerThread = new Thread(new ThreadStart(WorkerLoop));
    _workerThread.IsBackground = true;
    _workerThread.Start();
}

private void WorkerLoop()
{
    while(true)
    {
        _clientSocket = _tcpServer.AcceptSocket();
        _networkStream = new NetworkStream(_clientSocket, true);
        /* ... rest of method here ... */
    }
}

I'm attempting the following code in the iOSSimulator using XCode 4.2 and targeting iOS 5. The Mac that's hosting the simulator is on the same network as the server program and I can run a Java client that uses the same hardcoded local IP as below to connect just fine. In the Objective C code, I'm receiving some data and storing it in an NSData member property, then once the Socket is opened, I use the stream callback to tell me when to try sending data.

- (IBAction)connectToServer  
{
    NSURL *serverUrl = [NSURL URLWithString:@"10.0.0.5"];

    CFReadStreamRef readStream;
    CFWriteStreamRef writeStream;
    CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)[serverUrl host], 8086, &readStream, &writeStream);

    [self setInStream:(NSInputStream *)readStream];
    [self setOutStream:(NSOutputStream *)writeStream];
    [self.inStream setDelegate:self];
    [self.outStream setDelegate:self];
    [self.inStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.inStream open];
    [self.outStream open];

    NSError *error = [self.outStream streamError];
    if (error) {
        NSLog(@"outstream error: %@", [error localizedDescription]);
    }
}

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
    NSError *error;
    if ([aStream isEqual:outStream]) {
        switch (eventCode) {
            case NSStreamEventHasSpaceAvailable:
                NSLog(@"Stream has space!");
                [self writeDataToStream];
                break;
            case NSStreamEventOpenCompleted:
                NSLog(@"Stream is open!");
                break;
            case NSStreamEventErrorOccurred:
                error = [self.outStream streamError];
                NSLog(@"Stream error occured: %@", [error localizedDescription]);
                break;
            default:
                break;
        }
    }
}

- (void)writeDataToStream
{
    unsigned int byteIndex = 0;
    unsigned int length = data.length;
    uint8_t *buffer = (uint8_t *)[data bytes];

    while (byteIndex <= length) {    
        unsigned int bufferLength = (length - byteIndex >= 1024) ? 1024 : (length - byteIndex);
        uint8_t tempBuffer[bufferLength];

        (void)memcpy(tempBuffer, buffer, bufferLength);
        if (self.outStream.hasSpaceAvailable) {
            bufferLength = [self.outStream write:tempBuffer maxLength:bufferLength];
            byteIndex += bufferLength;
        } else
            NSLog(@"Stream is blocked!");
    }
}

In the XCode console, I see "Stream is open!", followed by "Stream has space!", followed by an exception that says "The operation couldn't be completed. Bad file descriptor". I placed a breakpoint in my server code right after _tcpServer.AcceptSocket(), but it never hits. It seems that the stream opens, but the socket never connects?

You didn't indicate, but did you step through to see if you actually wrote anything to the socket? If you didn't, then your bufferLength variable becomes a -1. This will then continuously loop (because byteIndex never becomes larger than length! At some point your (length - byteIndex) will go less than 1 and THAT is where I suspect things are tossing cookies. — Feloneous Cat, Apr 20 '12 at 14:06
Another thing that helps in network applications is to run a packet sniffer (wireshark or even CocoaPacketAnalyzer) helps immensely. Then you don't have to guess why things aren't working. — Feloneous Cat, Apr 20 '12 at 14:08

score -1 · Answer 1 · edited Oct 21 '12 at 07:46

-1

Try to check [serverUrl host] if it is nil.

I encountered this problem as well, so what I did was adding a http:// protocol string before the IP address (URLWithString:@"http://10.0.0.5").

edited Oct 21 '12 at 07:46

Guntis Treulands

4,764
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answered Jun 04 '12 at 09:57

morph85

807
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18

He isn't using http protocol. So, no need to add http prefix. – fyasar Apr 06 '13 at 14:24
I was simply pointing out the mistake that there could be error in NSURL to be nil. (Reference: developer.apple.com/library/mac/#documentation/Cocoa/Reference/… section "Handling Object Creation Failure" where you will need to conform to RFC 2396 for file path or RFC 1808 for http URL and specify a scheme). Otherwise create CFString or NSString instead. If you're using CFURL or NSURL without scheme, there is high possibility you will be getting a nil. – morph85 Jun 30 '13 at 11:39

Socket issues between iOS and .NET?

1 Answers1