Talking to sockets through dispatch_io_read

gistfile1.m

//
//  ACAppDelegate.m
//  SocketTest
//
//  Created by Izzy Fraimow on 11/19/12.
//

#import "ACAppDelegate.h"

#include <arpa/inet.h>

@interface ACAppDelegate ()
@property (nonatomic, assign) BOOL serverStarted;
@property (nonatomic, assign) BOOL listening;
@property (nonatomic, strong) NSOutputStream *writeSocket;
@end

@implementation ACAppDelegate

// StringFromDispatchData() from Mike Ash's
// [Friday Q&A 2011-10-14: What's New in GCD](http://www.mikeash.com/pyblog/friday-qa-2011-10-14-whats-new-in-gcd.html)
NSString *StringFromDispatchData(dispatch_data_t data) {
	NSMutableString *s = [NSMutableString stringWithCapacity: dispatch_data_get_size(data)];
	dispatch_data_apply(data, ^(dispatch_data_t region, size_t offset, const void *buffer, size_t size) {
		[s appendFormat: @"%.*s", size, buffer];
		return (_Bool)true;
	});
	return s;
}

static struct sockaddr_in serverAddress;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification; {
	bzero((char *)&serverAddress, sizeof(serverAddress));
	serverAddress.sin_len = sizeof(serverAddress);
	serverAddress.sin_family = AF_INET;
	serverAddress.sin_port = htons(2000);
	serverAddress.sin_addr.s_addr = inet_addr("127.0.0.1");
	
	self.serverStarted = NO;
	self.listening = NO;
}

- (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication *)sender; {
	// probably tear down sockets here... or something
	return NSTerminateNow;
}

- (IBAction)startListening:(id)sender; {
	@synchronized(self) {
		if(!self.serverStarted) {
			NSLog(@"start the server first, man!");
			return;
		}
		
		if(self.listening) {
			NSLog(@"Bad!");
			return;
		}
		
		dispatch_fd_t readSocket = socket(AF_INET, SOCK_STREAM, 0);
		if (readSocket == -1) {
			NSLog(@"socket(AF_INET, SOCK_STREAM, 0) failed");
			self.listening = NO;
			return;
		}
		
		if (connect(readSocket, (const struct sockaddr *)&serverAddress, serverAddress.sin_len) == -1) {
			NSLog(@"Could not connect: %u", errno);
			self.listening = NO;
			return;
		}
		
		dispatch_io_t socketChannel = dispatch_io_create(DISPATCH_IO_STREAM, readSocket, dispatch_get_global_queue(0, 0), ^(int error) {
			if(error) fprintf(stderr, "got an error from stdin: %d (%s)\n", error, strerror(error));
		});
		
		dispatch_io_set_low_water(socketChannel, 1);
				
		__weak ACAppDelegate *weakSelf = self;
		dispatch_io_read(socketChannel, 0, SIZE_MAX, dispatch_get_global_queue(0, 0), ^(bool done, dispatch_data_t data, int error) {
			if(data) {
				NSString *dataString = StringFromDispatchData(data);
				NSLog(@"Read data: %@ at time: %@", dataString, [NSDate date]);
			}
			
			if(error) {
				NSLog(@":(");
				weakSelf.listening = NO;
			}
			
			if(done) {
				NSLog(@"Done!");
				weakSelf.listening = NO;
			}
		});
		
		self.listening = YES;
	}
}

- (IBAction)startSocket:(id)sender; {
	@synchronized(self) {
		if(self.serverStarted) {
			NSLog(@"Wtf man?");
			return;
		}
		
		dispatch_fd_t writeSocket = socket(AF_INET, SOCK_STREAM, 0);
		if (writeSocket == -1) {
			NSLog(@"socket(AF_INET, SOCK_STREAM, 0) failed");
			self.serverStarted = NO;
			return;
		}
		
		bind(writeSocket, (struct sockaddr *) &serverAddress, serverAddress.sin_len);
		listen(writeSocket, 1024);
		
		__weak ACAppDelegate *weakSelf = self;
		dispatch_async(dispatch_get_global_queue(0, 0), ^{
			int connectionSocket;
			while (1) {
							
				if ((connectionSocket = accept(writeSocket, NULL, NULL)) < 0 ) {
					NSLog(@"ECHOSERV: Error calling accept(): %u", errno);
					weakSelf.serverStarted = NO;
					exit(EXIT_FAILURE);
				}
				
				// Uncomment while for NEVER ENDING FUN
				//while(1 && connectionSocket) {
					if ( write(connectionSocket, "Hello!", strlen("Hello!")) <= 0 ) {
						NSLog(@"ECHOSERV: Error calling write(): %u", errno);
						weakSelf.serverStarted = NO;
					}
					
					sleep(1);
				//}
				
				if ( close(connectionSocket) < 0 ) {
					NSLog(@"ECHOSERV: Error calling close(): %u", errno);
					weakSelf.serverStarted = NO;
					exit(EXIT_FAILURE);
				}
			}
		});
		
		self.serverStarted = YES;
	}
}

@end