Question

I need some help in IOS Socket programming. I have implemented a successful TCP Socket connection between IOS and a Java Server, however I found that it is imposible to reconnect it after the socket fails (I disconnect my network and reconnect it).

That’s the code I use to open the streams:

- (void)initCommunication{
@try {
    CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)@"XXX.XXX.XXX.XXX", 4454, &readStream, &writeStream);

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

    //Asignamos los delegates
    inputStream.delegate = self;
    outputStream.delegate = self;  

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

    [inputStream open];
    [outputStream open];
    connected = true;
    }
}
@catch (NSException *exception) {
    connected = false;
    NSLog(@"Error connecting socket: %@", exception.reason);
    [self checkConnection];
}
}

And when I receive a NSStreamEventErrorOccurred or a NSStreamEventEndEncountered I try to close the connection and reconnect again.

I close it with:

-(void) close{

[inputStream close];
[inputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[outputStream close];
[outputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[inputStream setDelegate:nil];
inputStream = nil;
[outputStream setDelegate:nil];
outputStream = nil;

connected = false;
}

The problem is that the socket is not reconnecting again… I am thinking on using SmallSockets or CocoaAsyncSockets to see if I can reconnect the socket… Do you see any implementation problem? Do you recommend using SmallSockets or CocoaAsyncSockets??

Thank you in advance!!

Answer 1

Finally I did implement it with CocoaAsyncSockets https://github.com/robbiehanson/CocoaAsyncSocket and it was really easy doing a reconnection with this socket.

First I initialize the socket object:

socket = [[GCDAsyncSocket alloc] initWithDelegate:self delegateQueue:dispatch_get_main_queue()];

To connect I use:

NSError *err = nil;
if ([socket connectToHost:@"XXX.XXX.XXX.XXX" onPort:YYYY error:&err])
{
NSLog(@"Connection performed!");
}
else
{
NSLog(@"Unable to connect: %@", err);
}

And then you can use the delegate to do reconnection whenever it failed:

- (void)socket:(GCDAsyncSocket *)sock didConnectToHost:(NSString *)host port:(UInt16)port
{
NSLog(@"Socket:DidConnectToHost: %@ Port: %hu", host, port);

connected = YES;
    [sock readDataWithTimeout:-1 tag:0];
}

- (void)socketDidDisconnect:(GCDAsyncSocket *)sock withError:(NSError *)err
{
NSLog(@"SocketDidDisconnect:WithError: %@", err);   
    connected = NO;
    //We will try to reconnect
    [self checkConnection];
}

- (void)socket:(GCDAsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag
{
    [self processReceivedData:data];
    [sock readDataWithTimeout:-1 tag:0];
}  

I found very easy to use that library. I hope that helps anyone.
Thanks a lot.