MQTTClient is an Objective-C wrapper for libmosquitto. MQTTClient supports authentication and TLS encryption.
MQTTClient has been tested with libmosquitto 1.4.1. Download the latest libmosquitto here: http://mosquitto.org/download/

Add MQTTClient.h and MQTTClient.m to your project.

Add the libmosquitto source from the link above to your project.

Compile openssl for iOS using the instructions here:
https://github.com/x2on/OpenSSL-for-iPhone Add the compiled openssl framework to your project.

Create certificates for client and server using:
http://rockingdlabs.dunmire.org/exercises-experiments/ssl-client-certs-to-secure-mqtt

Add client.crt, client.key, and ca.crt to your project.

Set a preprocessor flag in XCode "WITH_TLS" by clicking the project in XCode then click the target then click build settings Search for preprocessor macros and add "WITH_TLS" to debug and release

Call init then connect then subscribe

-(id)initWithUsername:(NSString *)username 
             password:(NSString *)password 
               caCert:(NSString *)caCert 
           clientCert:(NSString *)clientCert 
            clientKey:(NSString *)clientKey;

-(void)connectToHost:(NSString *)host 
                port:(int)port
           keepAlive:(int)keepAlive;

-(void)subscribeToTopic:(NSString *)topic;

Add MQTTClient.h and MQTTClient.m to your project.
Add the libmosquitto source from the link above to your project.

Designate one of the objects as the MQTTClientDelegate There is one required method:

-(void)messageReceived:(NSData *)messageData onTopic:(NSString *)topic;

Call init then connect then subscribe.

-(id)init;

-(id)initWithUsername:(NSString *)username 
             password:(NSString *)password;

-(void)connectToHost:(NSString *)host 
                port:(int)port  
           keepAlive:(int)keepAlive;

-(void)subscribeToTopic:(NSString *)topic;