From e70e2367b6383173f3a9d91b7062ad9610f36759 Mon Sep 17 00:00:00 2001
From: Todd Treece <toddtreece@gmail.com>
Date: Mon, 5 Oct 2015 11:32:10 -0400
Subject: [PATCH] only check for suback if using MQTT 3.1.1 or higher

---
 Adafruit_MQTT.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Adafruit_MQTT.cpp b/Adafruit_MQTT.cpp
index d7e6fe1..302c47e 100644
--- a/Adafruit_MQTT.cpp
+++ b/Adafruit_MQTT.cpp
@@ -125,13 +125,16 @@ int8_t Adafruit_MQTT::connect() {
     if (!sendPacket(buffer, len))
       return -1;
 
-    // Get SUBACK
-    len = readPacket(buffer, 5, CONNECT_TIMEOUT_MS);
-    DEBUG_PRINT(F("SUBACK:\t"));
-    DEBUG_PRINTBUFFER(buffer, len);
-    if ((len != 5) || (buffer[0] != (MQTT_CTRL_SUBACK << 4))) {
-      return 6;  // failure to subscribe
+    // Check for SUBACK if using MQTT 3.1.1 or higher
+    if(MQTT_PROTOCOL_LEVEL > 3) {
+      len = readPacket(buffer, 5, CONNECT_TIMEOUT_MS);
+      DEBUG_PRINT(F("SUBACK:\t"));
+      DEBUG_PRINTBUFFER(buffer, len);
+      if ((len != 5) || (buffer[0] != (MQTT_CTRL_SUBACK << 4))) {
+        return 6;  // failure to subscribe
+      }
     }
+
   }
 
   return 0;