1. 下載MQTTKIT開源庫，編譯出你所需要的libMQTTKit.a和標頭檔案

MQTTKIT開源庫github下載地址：點這裡

下載好MQTTKIT開源庫後，編譯下（假如你想在模擬器上執行客戶端，可以直接編譯出一個模擬器版本的libMQTTKit.a和標頭檔案，反之編譯出一個手機客戶端版本）

編譯好的檔案截圖：

2. MQTT客戶端設計（連線伺服器，釋出話題，訂閱話題）

新建一個關於mqtt的xcode工程，然後將上面編譯好的libMQTTKit.a和標頭檔案拖到工程中去

然後新建一個類，用做連線測試用，具體程式碼如下：

（也可以參考這個github大神寫的demo：地址）

@implementation LJMQTTViewController

- (void)dealloc
{
    // disconnect the MQTT client
    [self.client disconnectWithCompletionHandler:^(NSUInteger code) {
        // The client is disconnected when this completion handler is called
        NSLog(@"MQTT is disconnected");
    }];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self initMqttSerive];
    [self createBulletButton];
}

- (void)createBulletButton
{
    UIButton *_ljBtn = [[UIButton alloc]init];
    [_ljBtn setFrame:CGRectMake((screenFrame.size.width - 150)/2.0, (screenFrame.size.height - 50)/2.0 + 120, 150, 50)];
    _ljBtn.backgroundColor = [UIColor grayColor];
    [_ljBtn setTitle:@"Bullet test" forState:UIControlStateNormal];
    [_ljBtn addTarget:self action:@selector(ljBulletBtnClicked) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_ljBtn];
}

- (void)initMqttSerive
{
    // create the MQTT client with an unique identifier
    NSString *clientID = [UIDevice currentDevice].identifierForVendor.UUIDString;
    self.client = [[MQTTClient alloc] initWithClientId:clientID];
    
    // keep a reference on the switch to avoid having a reference to self in the
    // block below (retain/release cycle, blah blah blah)
   // UISwitch *subSwitch = self.subscribedSwitch;
    
    // define the handler that will be called when MQTT messages are received by the client
    [self.client setMessageHandler:^(MQTTMessage *message) {
        // extract the switch status from the message payload
        BOOL on = [message.payloadString boolValue];
        
        // the MQTTClientDelegate methods are called from a GCD queue.
        // Any update to the UI must be done on the main queue
        dispatch_async(dispatch_get_main_queue(), ^{
            //[subSwitch setOn:on animated:YES];
        });
    }];
    
    // connect the MQTT client
    [self.client connectToHost:kMQTTServerHost completionHandler:^(MQTTConnectionReturnCode code) {
        if (code == ConnectionAccepted) {
            // The client is connected when this completion handler is called
            NSLog(@"client is connected with id %@", clientID);
            [self subscribeTop:kTopic];
        }
    }];
    
    //獲取話題訊息回撥
    //[self handleMqttMessage];
}

- (void)ljBulletBtnClicked
{
    [self publishString:@"test"];
}

#pragma mark -- 訂閱話題
- (void)subscribeTop:(NSString*)topicStr
{
    // Subscribe to the topic
    [self.client subscribe:topicStr withCompletionHandler:^(NSArray *grantedQos) {
        // The client is effectively subscribed to the topic when this completion handler is called
        NSLog(@"subscribed to topic %@", kTopic);
    }];
}

#pragma mark -- 釋出
- (void)publishString:(NSString*)payload
{
    // use the MQTT client to send a message with the switch status to the topic
    [self.client publishString:payload
                       toTopic:kTopic
                       withQos:AtMostOnce
                        retain:YES
             completionHandler:nil];
    // we passed nil to the completionHandler as we are not interested to know
    // when the message was effectively sent
}

#pragma mark -- received message
- (void)handleMqttMessage
{
    // define the handler that will be called when MQTT messages are received by the client
    [self.client setMessageHandler:^(MQTTMessage *message)
     {
        NSLog(@"received message %@", message.payloadString);
    }];
}
 

從上面的log可以看出，當你連線伺服器成功後，伺服器會給你返回一個唯一的id，當服務端想給你推訊息時，可以根據你的這個唯一id來推給你

我此處訂閱的話題是“#”，它代表伺服器上所有的話題訊息，我都可以接收到。

3. 通過PHP網頁來向客戶端傳送一個話題（此處的伺服器就是上一篇搭建的mosquitto）

PHP傳送訊息的截圖（http://localhost/PhpM/index.php）：

PHP的MQTT環境搭建見我的這篇文章：地址

IOS MQTT客戶端接收到的訊息截圖：