Added ALPN support

MQTTClient/MQTTClient/MQTTCFSocketTransport.h

@@ -42,6 +42,10 @@
 /// A Boolean value indicating whether the transport should send data over the cell network. Defaults to `YES`.
 @property (nonatomic) BOOL allowsCellularAccess;
 
+/** ALPN to use, default to not use ALPN
+ */
+@property (strong, nonatomic) NSArray *alpn;
+
 /** Require for VoIP background service
  * defaults to NO
  */

MQTTClient/MQTTClient/MQTTCFSocketTransport.m

@@ -27,13 +27,15 @@ @implementation MQTTCFSocketTransport
 @synthesize streamSSLLevel;
 @synthesize host;
 @synthesize port;
+@synthesize alpn;
 
 - (instancetype)init {
     self = [super init];
     self.host = @"localhost";
     self.port = 1883;
     self.tls = false;
     self.allowsCellularAccess = YES;
+    self.alpn = nil;
     self.voip = false;
     self.certificates = nil;
     self.queue = dispatch_get_main_queue();
@@ -95,8 +97,25 @@ - (void)open {
                                                code:errSSLInternal
                                            userInfo:@{NSLocalizedDescriptionKey : @"Fail to init ssl output stream!"}];
         }
+
+        if (@available(iOS 11, *)) {
+            if (self.alpn != nil && [self.alpn count] > 0) {
+                OSStatus err;
+                SSLContextRef sslContext = CFReadStreamCopyProperty(readStream, kCFStreamPropertySSLContext);
+                if ((err = SSLSetALPNProtocols(sslContext, (__bridge CFArrayRef) self.alpn))) {
+                    connectError = [NSError errorWithDomain:@"MQTT" code:err userInfo:@{
+                        NSLocalizedDescriptionKey : @"ALPN error"}];
+                }
+
+                sslContext = CFWriteStreamCopyProperty(writeStream, kCFStreamPropertySSLContext);
+                if ((err = SSLSetALPNProtocols(sslContext, (__bridge CFArrayRef) self.alpn))) {
+                    connectError = [NSError errorWithDomain:@"MQTT" code:err userInfo:@{
+                        NSLocalizedDescriptionKey : @"ALPN error"}];
+                }
+            }
+        }
     }
-    
+
     if (!self.allowsCellularAccess) {
         CFReadStreamSetProperty(readStream, kCFStreamPropertyNoCellular, kCFBooleanTrue);
         CFWriteStreamSetProperty(writeStream, kCFStreamPropertyNoCellular, kCFBooleanTrue);

MQTTClient/MQTTClient/MQTTSSLSecurityPolicyTransport.m

@@ -65,6 +65,23 @@ - (void)open {
                                                code:errSSLInternal
                                            userInfo:@{NSLocalizedDescriptionKey : @"Fail to init ssl output stream!"}];
         }
+
+        if (@available(iOS 11, *)) {
+            if (self.alpn != nil && [self.alpn count] > 0) {
+                OSStatus err;
+                SSLContextRef sslContext = CFReadStreamCopyProperty(readStream, kCFStreamPropertySSLContext);
+                if ((err = SSLSetALPNProtocols(sslContext, (__bridge CFArrayRef) self.alpn))) {
+                    connectError = [NSError errorWithDomain:@"MQTT" code:err userInfo:@{
+                        NSLocalizedDescriptionKey : @"ALPN error"}];
+                }
+
+                sslContext = CFWriteStreamCopyProperty(writeStream, kCFStreamPropertySSLContext);
+                if ((err = SSLSetALPNProtocols(sslContext, (__bridge CFArrayRef) self.alpn))) {
+                    connectError = [NSError errorWithDomain:@"MQTT" code:err userInfo:@{
+                        NSLocalizedDescriptionKey : @"ALPN error"}];
+                }
+            }
+        }
     }
 
     if (!connectError) {

MQTTClient/MQTTClient/MQTTSessionManager.h

@@ -90,6 +90,10 @@ typedef NS_ENUM(int, MQTTSessionManagerState) {
  */
 @property (readonly) UInt32 port;
 
+/** alpn to negotiate in TLS sessions
+ */
+@property (strong, nonatomic) NSArray *alpn;
+
 /** the delegate receiving incoming messages
  */
 @property (weak, nonatomic) id<MQTTSessionManagerDelegate> delegate;

MQTTClient/MQTTClient/MQTTSessionManager.m

@@ -354,6 +354,7 @@ - (void)connectToInternal:(MQTTConnectHandler)connectHandler {
         transport.voip = self.session.voip;
         transport.queue = self.queue;
         transport.streamSSLLevel = self.streamSSLLevel;
+        transport.alpn = self.alpn;
         self.session.transport = transport;
         [self.session connectWithConnectHandler:connectHandler];
     }