iOS WiFi Print

Printer.h

//
//  Printer.h
//  Print
//
//  Created by Graham Mueller on 10/27/15.
//  Copyright © 2015 Graham Mueller. All rights reserved.
//

#import <Foundation/Foundation.h>

typedef void (^GenericErrorCallback)(NSString *err)

@interface Printer : NSObject

- (id)initWithIPAddress:(NSString *)ipAddress port:(UInt32)port;
- (void)sendDataToPrinter:(NSData *)data callback:(GenericErrorCallback)callback;

@end

Printer.m

//
//  Printer.m
//  Print
//
//  Created by Graham Mueller on 10/27/15.
//  Copyright © 2015 Graham Mueller. All rights reserved.
//

#import "Printer.h"

@interface Printer () <NSStreamDelegate>

@property (strong, nonatomic) NSString *ipAddress;
@property (assign, nonatomic) UInt32 port;
@property (strong, nonatomic) NSOutputStream *outputStream;
@property (strong, nonatomic) NSData *documentData;

@property (copy, nonatomic) GenericErrorCallback callback;

@end

@implementation Printer

- (id)initWithIPAddress:(NSString *)ipAddress port:(UInt32)port {
    if (self = [super init]) {
        _ipAddress = ipAddress;
        _port = port;
    }
    
    return self;
}

- (void)sendDataToPrinter:(NSData *)data callback:(GenericErrorCallback)callback {
    self.callback = callback;
    self.documentData = data;
    
    // Open socket. Note that we're entirely ignoring the Input Stream.
    CFWriteStreamRef writeStream;
    CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)self.ipAddress, self.port, NULL, &writeStream);
    
    self.outputStream = (__bridge_transfer NSOutputStream *)writeStream;
    [self.outputStream setDelegate:self];
    [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outputStream open];
}

#pragma mark - Stream Delegate methods
- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)event {
    switch (event) {
        // Stream is ready for writing, send the print data
        case NSStreamEventHasSpaceAvailable:
            [self.outputStream write:self.documentData.bytes maxLength:self.documentData.length];
            self.callback(nil);
            [self.outputStream close];
            break;

        // Something error happen, let the user know
        case NSStreamEventErrorOccurred:
            self.callback([[self.outputStream streamError] localizedDescription]);
            [self.outputStream close];
            break;

        default: break;
    }
}

@end

This is the most direct and simple printing method via WiFi. It's by no means bullet proof, but it's enough to get something coming out.