An API for using MQTT over multiple transports

Dependencies:   FP MQTTPacket

Dependents:   Cellular_HelloMQTT IoTStarterKit GSwifiInterface_HelloMQTT IBMIoTClientEthernetExample ... more

This library is part of the EclipseTM Paho project; specifically the embedded client.

The goals of this API are:

  1. to be independent of any system library: hence templates parameters for networking, timer and threading classes
  2. not to rely on heap storage, only automatic (I think this is a good thing)
  3. to limit memory use, for instance by defining the size of the buffers and arrays used at object creation time

Files at this revision

API Documentation at this revision

Comitter:
icraggs
Date:
Mon Apr 28 16:07:51 2014 +0000
Parent:
19:57f6f976e878
Child:
21:e918525e529d
Commit message:
Split APIs into two. Add unsubscribe and disconnect processing

Changed in this revision

MQTTAsync.h Show annotated file Show diff for this revision Revisions of this file
MQTTClient.h Show annotated file Show diff for this revision Revisions of this file
MQTTPacket.lib Show annotated file Show diff for this revision Revisions of this file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MQTTAsync.h	Mon Apr 28 16:07:51 2014 +0000
@@ -0,0 +1,586 @@
+/*******************************************************************************
+ * Copyright (c) 2014 IBM Corp.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * and Eclipse Distribution License v1.0 which accompany this distribution.
+ *
+ * The Eclipse Public License is available at
+ *    http://www.eclipse.org/legal/epl-v10.html
+ * and the Eclipse Distribution License is available at
+ *   http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * Contributors:
+ *    Ian Craggs - initial API and implementation and/or initial documentation
+ *******************************************************************************/
+
+#if !defined(MQTTCLIENT_H)
+#define MQTTCLIENT_H
+
+#include "FP.h"
+#include "MQTTPacket.h"
+#include "stdio.h"
+
+namespace MQTT
+{
+
+
+enum QoS { QOS0, QOS1, QOS2 };
+
+
+struct Message
+{
+    enum QoS qos;
+    bool retained;
+    bool dup;
+    unsigned short id;
+    void *payload;
+    size_t payloadlen;
+};
+
+
+class PacketId
+{
+public:
+    PacketId();
+    
+    int getNext();
+   
+private:
+    static const int MAX_PACKET_ID = 65535;
+    int next;
+};
+
+typedef void (*messageHandler)(Message*);
+
+typedef struct limits
+{
+	int MAX_MQTT_PACKET_SIZE; // 
+	int MAX_MESSAGE_HANDLERS;  // each subscription requires a message handler
+	int MAX_CONCURRENT_OPERATIONS;  // each command which runs concurrently can have a result handler, when we are in multi-threaded mode
+	int command_timeout;
+		
+	limits()
+	{
+		MAX_MQTT_PACKET_SIZE = 100;
+		MAX_MESSAGE_HANDLERS = 5;
+		MAX_CONCURRENT_OPERATIONS = 1; // 1 indicates single-threaded mode - set to >1 for multithreaded mode
+		command_timeout = 30;
+	}
+} Limits;
+  
+  
+template<class Network, class Timer, class Thread, class Mutex> class Client
+{
+    
+public:    
+
+	struct Result
+	{
+    	/* success or failure result data */
+    	Client<Network, Timer, Thread, Mutex>* client;
+		int connack_rc;
+	};
+
+	typedef void (*resultHandler)(Result*);	
+   
+    Client(Network* network, const Limits limits = Limits()); 
+           
+    int connect(MQTTPacket_connectData* options = 0, resultHandler fn = 0);
+    
+     template<class T>
+    int connect(MQTTPacket_connectData* options = 0, T *item = 0, void(T::*method)(Result *) = 0);  // alternative to pass in pointer to member function
+        
+    int publish(const char* topic, Message* message, resultHandler rh = 0);
+    
+    int subscribe(const char* topicFilter, enum QoS qos, messageHandler mh, resultHandler rh = 0);
+    
+    int unsubscribe(const char* topicFilter, resultHandler rh = 0);
+    
+    int disconnect(int timeout, resultHandler rh = 0);
+    
+	void yield(int timeout);
+    
+private:
+
+    void run(void const *argument);
+    int cycle(int timeout);
+    int waitfor(int packet_type, Timer& atimer);
+	int keepalive();
+	int findFreeOperation();
+
+    int decodePacket(int* value, int timeout);
+    int readPacket(int timeout);
+    int sendPacket(int length, int timeout);
+	int deliverMessage(MQTTString* topic, Message* message);
+    
+    Thread* thread;
+    Network* ipstack;
+    
+    Limits limits;
+    
+    char* buf;  
+    char* readbuf;
+
+    Timer ping_timer, connect_timer;
+    unsigned int keepAliveInterval;
+	bool ping_outstanding;
+    
+    PacketId packetid;
+    
+    typedef FP<void, Result*> resultHandlerFP;    
+    resultHandlerFP connectHandler; 
+    
+    typedef FP<void, Message*> messageHandlerFP;
+    struct MessageHandlers
+    {
+    	const char* topic;
+    	messageHandlerFP fp;
+    } *messageHandlers;      // Message handlers are indexed by subscription topic
+    
+    // how many concurrent operations should we allow?  Each one will require a function pointer
+    struct Operations
+    {
+    	unsigned short id;
+    	resultHandlerFP fp;
+    	const char* topic;         // if this is a publish, store topic name in case republishing is required
+    	Message* message;    // for publish, 
+    	Timer timer;         // to check if the command has timed out
+    } *operations;           // result handlers are indexed by packet ids
+
+	static void threadfn(void* arg);
+    
+};
+
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> void MQTT::Client<Network, Timer, Thread, Mutex>::threadfn(void* arg)
+{
+    ((Client<Network, Timer, Thread, Mutex>*) arg)->run(NULL);
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> MQTT::Client<Network, Timer, Thread, Mutex>::Client(Network* network, Limits limits)  : limits(limits), packetid()
+{
+	this->thread = 0;
+	this->ipstack = network;
+	this->ping_timer = Timer();
+	this->ping_outstanding = 0;
+	   
+	// How to make these memory allocations portable?  I was hoping to avoid the heap
+	buf = new char[limits.MAX_MQTT_PACKET_SIZE];
+	readbuf = new char[limits.MAX_MQTT_PACKET_SIZE];
+	this->operations = new struct Operations[limits.MAX_CONCURRENT_OPERATIONS];
+	for (int i = 0; i < limits.MAX_CONCURRENT_OPERATIONS; ++i)
+		operations[i].id = 0;
+	this->messageHandlers = new struct MessageHandlers[limits.MAX_MESSAGE_HANDLERS];
+	for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
+		messageHandlers[i].topic = 0;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::sendPacket(int length, int timeout)
+{
+    int sent = 0;
+    
+    while (sent < length)
+        sent += ipstack->write(&buf[sent], length, timeout);
+	if (sent == length)
+	    ping_timer.countdown(this->keepAliveInterval); // record the fact that we have successfully sent the packet    
+    return sent;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::decodePacket(int* value, int timeout)
+{
+    char c;
+    int multiplier = 1;
+    int len = 0;
+	const int MAX_NO_OF_REMAINING_LENGTH_BYTES = 4;
+
+    *value = 0;
+    do
+    {
+        int rc = MQTTPACKET_READ_ERROR;
+
+        if (++len > MAX_NO_OF_REMAINING_LENGTH_BYTES)
+        {
+            rc = MQTTPACKET_READ_ERROR; /* bad data */
+            goto exit;
+        }
+        rc = ipstack->read(&c, 1, timeout);
+        if (rc != 1)
+            goto exit;
+        *value += (c & 127) * multiplier;
+        multiplier *= 128;
+    } while ((c & 128) != 0);
+exit:
+    return len;
+}
+
+
+/**
+ * If any read fails in this method, then we should disconnect from the network, as on reconnect
+ * the packets can be retried. 
+ * @param timeout the max time to wait for the packet read to complete, in milliseconds
+ * @return the MQTT packet type, or -1 if none
+ */
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::readPacket(int timeout) 
+{
+    int rc = -1;
+    MQTTHeader header = {0};
+    int len = 0;
+    int rem_len = 0;
+
+    /* 1. read the header byte.  This has the packet type in it */
+    if (ipstack->read(readbuf, 1, timeout) != 1)
+        goto exit;
+
+    len = 1;
+    /* 2. read the remaining length.  This is variable in itself */
+    decodePacket(&rem_len, timeout);
+    len += MQTTPacket_encode(readbuf + 1, rem_len); /* put the original remaining length back into the buffer */
+
+    /* 3. read the rest of the buffer using a callback to supply the rest of the data */
+    if (ipstack->read(readbuf + len, rem_len, timeout) != rem_len)
+        goto exit;
+
+    header.byte = readbuf[0];
+    rc = header.bits.type;
+exit:
+    return rc;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::deliverMessage(MQTTString* topic, Message* message)
+{
+	int rc = -1;
+
+	// we have to find the right message handler - indexed by topic
+	for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
+	{
+		if (messageHandlers[i].topic != 0 && MQTTPacket_equals(topic, (char*)messageHandlers[i].topic))
+		{
+			messageHandlers[i].fp(message);
+			rc = 0;
+			break;
+		}
+	}
+	
+	return rc;
+}
+
+
+
+template<class Network, class Timer, class Thread, class Mutex> void MQTT::Client<Network, Timer, Thread, Mutex>::yield(int timeout)
+{
+	Timer atimer = Timer();
+	
+	atimer.countdown_ms(timeout);
+	while (!atimer.expired())
+		cycle(atimer.left_ms());
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::cycle(int timeout)
+{
+    /* get one piece of work off the wire and one pass through */
+
+    // read the socket, see what work is due
+    int packet_type = readPacket(timeout);
+    
+	int len, rc;
+    switch (packet_type)
+    {
+        case CONNACK:
+			if (this->thread)
+			{
+				Result res = {this, 0};
+            	if (MQTTDeserialize_connack(&res.connack_rc, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+                	;
+				connectHandler(&res);
+				connectHandler.detach(); // only invoke the callback once
+			}
+			break;
+        case PUBACK:
+        	if (this->thread)
+        		; //call resultHandler
+        case SUBACK:
+            break;
+        case PUBLISH:
+			MQTTString topicName;
+			Message msg;
+			rc = MQTTDeserialize_publish((int*)&msg.dup, (int*)&msg.qos, (int*)&msg.retained, (int*)&msg.id, &topicName,
+								 (char**)&msg.payload, (int*)&msg.payloadlen, readbuf, limits.MAX_MQTT_PACKET_SIZE);;
+			if (msg.qos == QOS0)
+				deliverMessage(&topicName, &msg);
+            break;
+        case PUBREC:
+   	        int type, dup, mypacketid;
+   	        if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+   	            ; 
+   	        // must lock this access against the application thread, if we are multi-threaded
+			len = MQTTSerialize_ack(buf, limits.MAX_MQTT_PACKET_SIZE, PUBREL, 0, mypacketid);
+		    rc = sendPacket(len, timeout); // send the PUBREL packet
+			if (rc != len) 
+				goto exit; // there was a problem
+
+            break;
+        case PUBCOMP:
+            break;
+        case PINGRESP:
+			ping_outstanding = false;
+            break;
+    }
+	keepalive();
+exit:
+    return packet_type;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::keepalive()
+{
+	int rc = 0;
+
+	if (keepAliveInterval == 0)
+		goto exit;
+
+	if (ping_timer.expired())
+	{
+		if (ping_outstanding)
+			rc = -1;
+		else
+		{
+			int len = MQTTSerialize_pingreq(buf, limits.MAX_MQTT_PACKET_SIZE);
+			rc = sendPacket(len, 1000); // send the ping packet
+			if (rc != len) 
+				rc = -1; // indicate there's a problem
+			else
+				ping_outstanding = true;
+		}
+	}
+
+exit:
+	return rc;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> void MQTT::Client<Network, Timer, Thread, Mutex>::run(void const *argument)
+{
+	while (true)
+		cycle(ping_timer.left_ms());
+}
+
+
+// only used in single-threaded mode where one command at a time is in process
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::waitfor(int packet_type, Timer& atimer)
+{
+	int rc = -1;
+	
+	do
+    {
+		if (atimer.expired()) 
+			break; // we timed out
+	}
+	while ((rc = cycle(atimer.left_ms())) != packet_type);	
+	
+	return rc;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::connect(MQTTPacket_connectData* options, resultHandler resultHandler)
+{
+	connect_timer.countdown(limits.command_timeout);
+
+    MQTTPacket_connectData default_options = MQTTPacket_connectData_initializer;
+    if (options == 0)
+        options = &default_options; // set default options if none were supplied
+    
+    this->keepAliveInterval = options->keepAliveInterval;
+	ping_timer.countdown(this->keepAliveInterval);
+    int len = MQTTSerialize_connect(buf, limits.MAX_MQTT_PACKET_SIZE, options);
+    int rc = sendPacket(len, connect_timer.left_ms()); // send the connect packet
+	if (rc != len) 
+		goto exit; // there was a problem
+    
+    if (resultHandler == 0)     // wait until the connack is received 
+    {
+        // this will be a blocking call, wait for the connack
+		if (waitfor(CONNACK, connect_timer) == CONNACK)
+		{
+        	int connack_rc = -1;
+        	if (MQTTDeserialize_connack(&connack_rc, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+	        	rc = connack_rc;
+	    }
+    }
+    else
+    {
+        // set connect response callback function
+        connectHandler.attach(resultHandler);
+        
+        // start background thread            
+        this->thread = new Thread((void (*)(void const *argument))&MQTT::Client<Network, Timer, Thread, Mutex>::threadfn, (void*)this);
+    }
+    
+exit:
+    return rc;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::findFreeOperation()
+{
+	int found = -1;
+	for (int i = 0; i < limits.MAX_CONCURRENT_OPERATIONS; ++i)
+	{
+		if (operations[i].id == 0)
+		{
+			found = i;
+			break;
+		}
+	}
+	return found;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::subscribe(const char* topicFilter, enum QoS qos, messageHandler messageHandler, resultHandler resultHandler)
+{
+	int index = 0;
+	if (this->thread)
+		index = findFreeOperation();	
+	Timer& atimer = operations[index].timer;
+	
+	atimer.countdown(limits.command_timeout);
+    MQTTString topic = {(char*)topicFilter, 0, 0};
+    
+    int len = MQTTSerialize_subscribe(buf, limits.MAX_MQTT_PACKET_SIZE, 0, packetid.getNext(), 1, &topic, (int*)&qos);
+    int rc = sendPacket(len, atimer.left_ms()); // send the subscribe packet
+	if (rc != len) 
+		goto exit; // there was a problem
+    
+    /* wait for suback */
+    if (resultHandler == 0)
+    {
+        // this will block
+        if (waitfor(SUBACK, atimer) == SUBACK)
+        {
+            int count = 0, grantedQoS = -1, mypacketid;
+            if (MQTTDeserialize_suback(&mypacketid, 1, &count, &grantedQoS, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+                rc = grantedQoS; // 0, 1, 2 or 0x80 
+            if (rc != 0x80)
+            {
+            	for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
+				{
+					if (messageHandlers[i].topic == 0)
+					{
+						messageHandlers[i].topic = topicFilter;
+						messageHandlers[i].fp.attach(messageHandler);
+						rc = 0;
+						break;
+					}
+				}
+            }
+        }
+    }
+    else
+    {
+        // set subscribe response callback function
+        
+    }
+    
+exit:
+    return rc;
+}
+
+
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::unsubscribe(const char* topicFilter, resultHandler resultHandler)
+{
+	int index = 0;
+	if (this->thread)
+		index = findFreeOperation();	
+	Timer& atimer = operations[index].timer;
+
+	atimer.countdown(limits.command_timeout);
+    MQTTString topic = {(char*)topicFilter, 0, 0};
+    
+    int len = MQTTSerialize_unsubscribe(buf, limits.MAX_MQTT_PACKET_SIZE, 0, packetid.getNext(), 1, &topic);
+    int rc = sendPacket(len, atimer.left_ms()); // send the subscribe packet
+	if (rc != len) 
+		goto exit; // there was a problem
+    
+    /* wait for unsuback */
+    if (resultHandler == 0)
+    {
+        // this will block
+        if (waitfor(UNSUBACK) == UNSUBACK)
+        {
+            int mypacketid;
+            if (MQTTDeserialize_unsuback(&mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+                rc = 0; 
+        }
+    }
+    else
+    {
+        // set unsubscribe response callback function
+        
+    }
+    
+exit:
+    return rc;
+}
+
+
+   
+template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::publish(const char* topicName, Message* message, resultHandler resultHandler)
+{
+	int index = 0;
+	if (this->thread)
+		index = findFreeOperation();	
+	Timer& atimer = operations[index].timer;
+
+	atimer.countdown(limits.command_timeout);
+    MQTTString topic = {(char*)topicName, 0, 0};
+
+	if (message->qos == QOS1 || message->qos == QOS2)
+		message->id = packetid.getNext();
+    
+	int len = MQTTSerialize_publish(buf, limits.MAX_MQTT_PACKET_SIZE, 0, message->qos, message->retained, message->id, topic, (char*)message->payload, message->payloadlen);
+    int rc = sendPacket(len, atimer.left_ms()); // send the subscribe packet
+	if (rc != len) 
+		goto exit; // there was a problem
+    
+    /* wait for acks */
+    if (resultHandler == 0)
+    {
+ 		if (message->qos == QOS1)
+		{
+	        if (waitfor(PUBACK, atimer) == PUBACK)
+    	    {
+    	        int type, dup, mypacketid;
+    	        if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+    	            rc = 0; 
+    	    }
+		}
+		else if (message->qos == QOS2)
+		{
+	        if (waitfor(PUBCOMP, atimer) == PUBCOMP)
+	   	    {
+	   	    	int type, dup, mypacketid;
+            	if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+    	           	rc = 0; 
+			}
+
+		}
+    }
+    else
+    {
+        // set publish response callback function
+        
+    }
+    
+exit:
+    return rc;
+}
+
+
+#endif
--- a/MQTTClient.h	Mon Apr 14 21:58:58 2014 +0100
+++ b/MQTTClient.h	Mon Apr 28 16:07:51 2014 +0000
@@ -39,6 +39,13 @@
 };
 
 
+struct MessageData
+{
+    struct Message message;
+    char* topicName;
+};
+
+
 class PacketId
 {
 public:
@@ -55,66 +62,105 @@
 
 typedef struct limits
 {
-	int MAX_MQTT_PACKET_SIZE; // 
-	int MAX_MESSAGE_HANDLERS;  // each subscription requires a message handler
-	int MAX_CONCURRENT_OPERATIONS;  // each command which runs concurrently can have a result handler, when we are in multi-threaded mode
-	int command_timeout;
-		
-	limits()
-	{
-		MAX_MQTT_PACKET_SIZE = 100;
-		MAX_MESSAGE_HANDLERS = 5;
-		MAX_CONCURRENT_OPERATIONS = 1; // 1 indicates single-threaded mode - set to >1 for multithreaded mode
-		command_timeout = 30;
-	}
+    int MAX_MQTT_PACKET_SIZE; // 
+    int MAX_MESSAGE_HANDLERS;  // each subscription requires a message handler
+    long command_timeout_ms;
+        
+    limits()
+    {
+        MAX_MQTT_PACKET_SIZE = 100;
+        MAX_MESSAGE_HANDLERS = 5;
+        command_timeout_ms = 30000;
+    }
 } Limits;
   
   
-template<class Network, class Timer, class Thread, class Mutex> class Client
+template<class Network, class Timer> class Client
 {
     
 public:    
 
-	struct Result
-	{
-    	/* success or failure result data */
-    	Client<Network, Timer, Thread, Mutex>* client;
-		int connack_rc;
-	};
-
-	typedef void (*resultHandler)(Result*);	
-   
+    /** Construct the client
+     *  @param network - pointer to an instance of the Network class - must be connected to the endpoint
+     *      before calling MQTT connect
+     *  @param limits an instance of the Limit class - to alter limits as required
+     */
     Client(Network* network, const Limits limits = Limits()); 
-           
-    int connect(MQTTPacket_connectData* options = 0, resultHandler fn = 0);
+    
+    typedef struct
+    {
+        Client* client;
+        Network* network;
+    } connectionLostInfo;
+    
+    typedef int (*connectionLostHandlers)(connectionLostInfo*);
+    
+    /** Set the connection lost callback - called whenever the connection is lost and we should be connected
+     *  @param clh - pointer to the callback function
+     */
+    void setConnectionLostHandler(connectionLostHandlers clh)
+    {
+        connectionLostHandler.attach(clh);
+    }
+    
+    /** Set the default message handling callback - used for any message which does not match a subscription message handler
+     *  @param mh - pointer to the callback function
+     */
+    void setDefaultMessageHandler(messageHandler mh)
+    {
+        defaultMessageHandler.attach(mh);
+    }
     
-     template<class T>
-    int connect(MQTTPacket_connectData* options = 0, T *item = 0, void(T::*method)(Result *) = 0);  // alternative to pass in pointer to member function
-        
-    int publish(const char* topic, Message* message, resultHandler rh = 0);
-    
-    int subscribe(const char* topicFilter, enum QoS qos, messageHandler mh, resultHandler rh = 0);
-    
-    int unsubscribe(const char* topicFilter, resultHandler rh = 0);
+    /** MQTT Connect - send an MQTT connect packet down the network and wait for a Connack
+     *  The nework object must be connected to the network endpoint before calling this 
+     *  @param options - connect options
+     *  @return success code -  
+     */       
+    int connect(MQTTPacket_connectData* options = 0);
+      
+    /** MQTT Publish - send an MQTT publish packet and wait for all acks to complete for all QoSs
+     *  @param topic - the topic to publish to
+     *  @param message - the message to send
+     *  @return success code -  
+     */      
+    int publish(const char* topicName, Message* message);
+   
+    /** MQTT Subscribe - send an MQTT subscribe packet and wait for the suback
+     *  @param topicFilter - a topic pattern which can include wildcards
+     *  @param qos - the MQTT QoS to subscribe at
+     *  @param mh - the callback function to be invoked when a message is received for this subscription
+     *  @return success code -  
+     */   
+    int subscribe(const char* topicFilter, enum QoS qos, messageHandler mh);
     
-    int disconnect(int timeout, resultHandler rh = 0);
-    
-	void yield(int timeout);
+    /** MQTT Unsubscribe - send an MQTT unsubscribe packet and wait for the unsuback
+     *  @param topicFilter - a topic pattern which can include wildcards
+     *  @return success code -  
+     */   
+    int unsubscribe(const char* topicFilter);
+    
+    /** MQTT Disconnect - send an MQTT disconnect packet 
+     *  @return success code -  
+     */
+    int disconnect();
     
-private:
-
-    void run(void const *argument);
-    int cycle(int timeout);
-    int waitfor(int packet_type, Timer& atimer);
-	int keepalive();
-	int findFreeOperation();
+    /** A call to this API must be made within the keepAlive interval to keep the MQTT connection alive
+     *  yield can be called if no other MQTT operation is needed.  This will also allow messages to be 
+     *  received.
+     */
+    void yield(int timeout);
+    
+private:
+
+    int cycle(Timer& timer);
+    int waitfor(int packet_type, Timer& timer);
+    int keepalive();
 
     int decodePacket(int* value, int timeout);
-    int readPacket(int timeout);
-    int sendPacket(int length, int timeout);
-	int deliverMessage(MQTTString* topic, Message* message);
+    int readPacket(Timer& timer);
+    int sendPacket(int length, Timer& timer);
+    int deliverMessage(MQTTString* topic, Message* message);
     
-    Thread* thread;
     Network* ipstack;
     
     Limits limits;
@@ -122,82 +168,63 @@
     char* buf;  
     char* readbuf;
 
-    Timer ping_timer, connect_timer;
+    Timer ping_timer;
     unsigned int keepAliveInterval;
-	bool ping_outstanding;
+    bool ping_outstanding;
     
     PacketId packetid;
     
-    typedef FP<void, Result*> resultHandlerFP;    
-    resultHandlerFP connectHandler; 
-    
     typedef FP<void, Message*> messageHandlerFP;
     struct MessageHandlers
     {
-    	const char* topic;
-    	messageHandlerFP fp;
+        const char* topic;
+        messageHandlerFP fp;
     } *messageHandlers;      // Message handlers are indexed by subscription topic
     
-    // how many concurrent operations should we allow?  Each one will require a function pointer
-    struct Operations
-    {
-    	unsigned short id;
-    	resultHandlerFP fp;
-    	const char* topic;         // if this is a publish, store topic name in case republishing is required
-    	Message* message;    // for publish, 
-    	Timer timer;         // to check if the command has timed out
-    } *operations;           // result handlers are indexed by packet ids
-
-	static void threadfn(void* arg);
+    messageHandlerFP defaultMessageHandler;
+    
+    typedef FP<int, connectionLostInfo*> connectionLostFP;
+    
+    connectionLostFP connectionLostHandler;
     
 };
 
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> void MQTT::Client<Network, Timer, Thread, Mutex>::threadfn(void* arg)
+template<class Network, class Timer> MQTT::Client<Network, Timer>::Client(Network* network, Limits limits)  : limits(limits), packetid()
 {
-    ((Client<Network, Timer, Thread, Mutex>*) arg)->run(NULL);
+    this->ipstack = network;
+    this->ping_timer = Timer();
+    this->ping_outstanding = 0;
+       
+    // How to make these memory allocations portable?  I was hoping to avoid the heap
+    buf = new char[limits.MAX_MQTT_PACKET_SIZE];
+    readbuf = new char[limits.MAX_MQTT_PACKET_SIZE];
+    this->messageHandlers = new struct MessageHandlers[limits.MAX_MESSAGE_HANDLERS];
+    for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
+        messageHandlers[i].topic = 0;
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> MQTT::Client<Network, Timer, Thread, Mutex>::Client(Network* network, Limits limits)  : limits(limits), packetid()
-{
-	this->thread = 0;
-	this->ipstack = network;
-	this->ping_timer = Timer();
-	this->ping_outstanding = 0;
-	   
-	// How to make these memory allocations portable?  I was hoping to avoid the heap
-	buf = new char[limits.MAX_MQTT_PACKET_SIZE];
-	readbuf = new char[limits.MAX_MQTT_PACKET_SIZE];
-	this->operations = new struct Operations[limits.MAX_CONCURRENT_OPERATIONS];
-	for (int i = 0; i < limits.MAX_CONCURRENT_OPERATIONS; ++i)
-		operations[i].id = 0;
-	this->messageHandlers = new struct MessageHandlers[limits.MAX_MESSAGE_HANDLERS];
-	for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
-		messageHandlers[i].topic = 0;
-}
-
-
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::sendPacket(int length, int timeout)
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::sendPacket(int length, Timer& timer)
 {
     int sent = 0;
     
     while (sent < length)
-        sent += ipstack->write(&buf[sent], length, timeout);
-	if (sent == length)
-	    ping_timer.countdown(this->keepAliveInterval); // record the fact that we have successfully sent the packet    
+        sent += ipstack->write(&buf[sent], length, timer.left_ms());
+    if (sent == length)
+        ping_timer.countdown(this->keepAliveInterval); // record the fact that we have successfully sent the packet    
     return sent;
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::decodePacket(int* value, int timeout)
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::decodePacket(int* value, int timeout)
 {
     char c;
     int multiplier = 1;
     int len = 0;
-	const int MAX_NO_OF_REMAINING_LENGTH_BYTES = 4;
+    const int MAX_NO_OF_REMAINING_LENGTH_BYTES = 4;
 
     *value = 0;
     do
@@ -226,7 +253,7 @@
  * @param timeout the max time to wait for the packet read to complete, in milliseconds
  * @return the MQTT packet type, or -1 if none
  */
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::readPacket(int timeout) 
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::readPacket(Timer& timer) 
 {
     int rc = -1;
     MQTTHeader header = {0};
@@ -234,16 +261,16 @@
     int rem_len = 0;
 
     /* 1. read the header byte.  This has the packet type in it */
-    if (ipstack->read(readbuf, 1, timeout) != 1)
+    if (ipstack->read(readbuf, 1, timer.left_ms()) != 1)
         goto exit;
 
     len = 1;
     /* 2. read the remaining length.  This is variable in itself */
-    decodePacket(&rem_len, timeout);
+    decodePacket(&rem_len, timer.left_ms());
     len += MQTTPacket_encode(readbuf + 1, rem_len); /* put the original remaining length back into the buffer */
 
     /* 3. read the rest of the buffer using a callback to supply the rest of the data */
-    if (ipstack->read(readbuf + len, rem_len, timeout) != rem_len)
+    if (ipstack->read(readbuf + len, rem_len, timer.left_ms()) != rem_len)
         goto exit;
 
     header.byte = readbuf[0];
@@ -253,174 +280,156 @@
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::deliverMessage(MQTTString* topic, Message* message)
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::deliverMessage(MQTTString* topic, Message* message)
 {
-	int rc = -1;
-;
-	// we have to find the right message handler - indexed by topic
-	for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
-	{
-		if (messageHandlers[i].topic && MQTTPacket_equals(topic, (char*)messageHandlers[i].topic))
-		{
-			messageHandlers[i].fp(message);
-			rc = 0;
-			break;
-		}
-	}
-	
-	return rc;
+    int rc = -1;
+
+    // we have to find the right message handler - indexed by topic
+    for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
+    {
+        if (messageHandlers[i].topic != 0 && MQTTPacket_equals(topic, (char*)messageHandlers[i].topic))
+        {
+            messageHandlers[i].fp(message);
+            rc = 0;
+            break;
+        }
+    }
+    if (rc == -1)
+        defaultMessageHandler(message);
+    
+    return rc;
 }
-
-
-
-template<class Network, class Timer, class Thread, class Mutex> void MQTT::Client<Network, Timer, Thread, Mutex>::yield(int timeout)
-{
-	Timer atimer = Timer();
-	
-	atimer.countdown_ms(timeout);
-	while (!atimer.expired())
-		cycle(atimer.left_ms());
-}
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::cycle(int timeout)
+
+template<class Network, class Timer> void MQTT::Client<Network, Timer>::yield(int timeout)
+{
+    Timer timer = Timer();
+    
+    timer.countdown_ms(timeout);
+    while (!timer.expired())
+        cycle(timer);
+}
+
+
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::cycle(Timer& timer)
 {
     /* get one piece of work off the wire and one pass through */
-   	printf("timeout %d\n", timeout); 
+
     // read the socket, see what work is due
-    int packet_type = readPacket(timeout);
+    int packet_type = readPacket(timer);
     
-	int len, rc;
+    int len, rc;
     switch (packet_type)
     {
         case CONNACK:
-			if (this->thread)
-			{
-				Result res = {this, 0};
-            	if (MQTTDeserialize_connack(&res.connack_rc, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-                	;
-				connectHandler(&res);
-				connectHandler.detach(); // only invoke the callback once
-			}
-			break;
         case PUBACK:
-        	if (this->thread)
-        		; //call resultHandler
         case SUBACK:
             break;
         case PUBLISH:
-			MQTTString topicName;
-			Message msg;
-			rc = MQTTDeserialize_publish((int*)&msg.dup, (int*)&msg.qos, (int*)&msg.retained, (int*)&msg.id, &topicName,
-								 (char**)&msg.payload, (int*)&msg.payloadlen, readbuf, limits.MAX_MQTT_PACKET_SIZE);;
-			if (msg.qos == QOS0)
-				deliverMessage(&topicName, &msg);
+            MQTTString topicName;
+            Message msg;
+            rc = MQTTDeserialize_publish((int*)&msg.dup, (int*)&msg.qos, (int*)&msg.retained, (int*)&msg.id, &topicName,
+                                 (char**)&msg.payload, (int*)&msg.payloadlen, readbuf, limits.MAX_MQTT_PACKET_SIZE);;
+            deliverMessage(&topicName, &msg);
+            if (msg.qos != QOS0)
+            {
+                if (msg.qos == QOS1)
+                    len = MQTTSerialize_ack(buf, limits.MAX_MQTT_PACKET_SIZE, PUBACK, 0, msg.id);
+                else if (msg.qos == QOS2)
+                    len = MQTTSerialize_ack(buf, limits.MAX_MQTT_PACKET_SIZE, PUBREC, 0, msg.id);
+                rc = sendPacket(len, timer); 
+                if (rc != len) 
+                    goto exit; // there was a problem
+            }
             break;
         case PUBREC:
-   	        int type, dup, mypacketid;
-   	        if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-   	            ; 
-   	        // must lock this access against the application thread, if we are multi-threaded
-			len = MQTTSerialize_ack(buf, limits.MAX_MQTT_PACKET_SIZE, PUBREL, 0, mypacketid);
-		    rc = sendPacket(len, timeout); // send the PUBREL packet
-			if (rc != len) 
-				goto exit; // there was a problem
+            int type, dup, mypacketid;
+            if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+                ; 
+            len = MQTTSerialize_ack(buf, limits.MAX_MQTT_PACKET_SIZE, PUBREL, 0, mypacketid);
+            rc = sendPacket(len, timer); // send the PUBREL packet
+            if (rc != len) 
+                goto exit; // there was a problem
 
             break;
         case PUBCOMP:
             break;
         case PINGRESP:
-			ping_outstanding = false;
+            ping_outstanding = false;
             break;
     }
-	keepalive();
+    keepalive();
 exit:
     return packet_type;
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::keepalive()
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::keepalive()
 {
-	int rc = 0;
+    int rc = 0;
 
-	if (keepAliveInterval == 0)
-		goto exit;
+    if (keepAliveInterval == 0)
+        goto exit;
 
-	if (ping_timer.expired())
-	{
-		if (ping_outstanding)
-			rc = -1;
-		else
-		{
-			int len = MQTTSerialize_pingreq(buf, limits.MAX_MQTT_PACKET_SIZE);
-			rc = sendPacket(len, 1000); // send the ping packet
-			if (rc != len) 
-				rc = -1; // indicate there's a problem
-			else
-				ping_outstanding = true;
-		}
-	}
+    if (ping_timer.expired())
+    {
+        if (ping_outstanding)
+            rc = -1;
+        else
+        {
+            Timer timer = Timer(1000);
+            int len = MQTTSerialize_pingreq(buf, limits.MAX_MQTT_PACKET_SIZE);
+            rc = sendPacket(len, timer); // send the ping packet
+            if (rc != len) 
+                rc = -1; // indicate there's a problem
+            else
+                ping_outstanding = true;
+        }
+    }
 
 exit:
-	return rc;
-}
-
-
-template<class Network, class Timer, class Thread, class Mutex> void MQTT::Client<Network, Timer, Thread, Mutex>::run(void const *argument)
-{
-	while (true)
-		cycle(ping_timer.left_ms());
+    return rc;
 }
 
 
 // only used in single-threaded mode where one command at a time is in process
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::waitfor(int packet_type, Timer& atimer)
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::waitfor(int packet_type, Timer& timer)
 {
-	int rc = -1;
-	
-	do
+    int rc = -1;
+    
+    do
     {
-		if (atimer.expired()) 
-			break; // we timed out
-	}
-	while ((rc = cycle(atimer.left_ms())) != packet_type);	
-	
-	return rc;
+        if (timer.expired()) 
+            break; // we timed out
+    }
+    while ((rc = cycle(timer)) != packet_type);  
+    
+    return rc;
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::connect(MQTTPacket_connectData* options, resultHandler resultHandler)
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::connect(MQTTPacket_connectData* options)
 {
-	connect_timer.countdown(limits.command_timeout);
+    Timer connect_timer = Timer(limits.command_timeout_ms);
 
     MQTTPacket_connectData default_options = MQTTPacket_connectData_initializer;
     if (options == 0)
         options = &default_options; // set default options if none were supplied
     
     this->keepAliveInterval = options->keepAliveInterval;
-	ping_timer.countdown(this->keepAliveInterval);
+    ping_timer.countdown(this->keepAliveInterval);
     int len = MQTTSerialize_connect(buf, limits.MAX_MQTT_PACKET_SIZE, options);
-    int rc = sendPacket(len, connect_timer.left_ms()); // send the connect packet
-	if (rc != len) 
-		goto exit; // there was a problem
+    int rc = sendPacket(len, connect_timer); // send the connect packet
+    if (rc != len) 
+        goto exit; // there was a problem
     
-    if (resultHandler == 0)     // wait until the connack is received 
+    // this will be a blocking call, wait for the connack
+    if (waitfor(CONNACK, connect_timer) == CONNACK)
     {
-        // this will be a blocking call, wait for the connack
-		if (waitfor(CONNACK, connect_timer) == CONNACK)
-		{
-        	int connack_rc = -1;
-        	if (MQTTDeserialize_connack(&connack_rc, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-	        	rc = connack_rc;
-	    }
-    }
-    else
-    {
-        // set connect response callback function
-        connectHandler.attach(resultHandler);
-        
-        // start background thread            
-        this->thread = new Thread((void (*)(void const *argument))&MQTT::Client<Network, Timer, Thread, Mutex>::threadfn, (void*)this);
+        int connack_rc = -1;
+        if (MQTTDeserialize_connack(&connack_rc, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+            rc = connack_rc;
     }
     
 exit:
@@ -428,101 +437,64 @@
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::findFreeOperation()
-{
-	int found = -1;
-	for (int i = 0; i < limits.MAX_CONCURRENT_OPERATIONS; ++i)
-	{
-		if (operations[i].id == 0)
-		{
-			found = i;
-			break;
-		}
-	}
-	return found;
-}
-
-
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::subscribe(const char* topicFilter, enum QoS qos, messageHandler messageHandler, resultHandler resultHandler)
-{
-	int index = 0;
-	if (this->thread)
-		index = findFreeOperation();	
-	Timer& atimer = operations[index].timer;
-	
-	atimer.countdown(limits.command_timeout);
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::subscribe(const char* topicFilter, enum QoS qos, messageHandler messageHandler)
+{ 
+    int len = -1;
+    Timer timer = Timer(limits.command_timeout_ms);
+    
     MQTTString topic = {(char*)topicFilter, 0, 0};
     
-    int len = MQTTSerialize_subscribe(buf, limits.MAX_MQTT_PACKET_SIZE, 0, packetid.getNext(), 1, &topic, (int*)&qos);
-    int rc = sendPacket(len, atimer.left_ms()); // send the subscribe packet
-	if (rc != len) 
-		goto exit; // there was a problem
+    int rc = MQTTSerialize_subscribe(buf, limits.MAX_MQTT_PACKET_SIZE, 0, packetid.getNext(), 1, &topic, (int*)&qos);
+    if (rc <= 0)
+        goto exit;
+    len = rc;
+    if ((rc = sendPacket(len, timer)) != len) // send the subscribe packet
+        goto exit; // there was a problem
     
-    /* wait for suback */
-    if (resultHandler == 0)
+    if (waitfor(SUBACK, timer) == SUBACK)      // wait for suback 
     {
-        // this will block
-        if (waitfor(SUBACK, atimer) == SUBACK)
+        int count = 0, grantedQoS = -1, mypacketid;
+        if (MQTTDeserialize_suback(&mypacketid, 1, &count, &grantedQoS, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+            rc = grantedQoS; // 0, 1, 2 or 0x80 
+        if (rc != 0x80)
         {
-            int count = 0, grantedQoS = -1, mypacketid;
-            if (MQTTDeserialize_suback(&mypacketid, 1, &count, &grantedQoS, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-                rc = grantedQoS; // 0, 1, 2 or 0x80 
-            if (rc != 0x80)
+            for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
             {
-            	for (int i = 0; i < limits.MAX_MESSAGE_HANDLERS; ++i)
-				{
-					if (messageHandlers[i].topic == 0)
-					{
-						messageHandlers[i].topic = topicFilter;
-						messageHandlers[i].fp.attach(messageHandler);
-						rc = 0;
-						break;
-					}
-				}
+                if (messageHandlers[i].topic == 0)
+                {
+                    messageHandlers[i].topic = topicFilter;
+                    messageHandlers[i].fp.attach(messageHandler);
+                    rc = 0;
+                    break;
+                }
             }
         }
     }
-    else
-    {
-        // set subscribe response callback function
-        
-    }
     
 exit:
     return rc;
 }
 
 
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::unsubscribe(const char* topicFilter, resultHandler resultHandler)
-{
-	int index = 0;
-	if (this->thread)
-		index = findFreeOperation();	
-	Timer& atimer = operations[index].timer;
-
-	atimer.countdown(limits.command_timeout);
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::unsubscribe(const char* topicFilter)
+{   
+    int len = -1;
+    Timer timer = Timer(limits.command_timeout_ms);
+    
     MQTTString topic = {(char*)topicFilter, 0, 0};
     
-    int len = MQTTSerialize_unsubscribe(buf, limits.MAX_MQTT_PACKET_SIZE, 0, packetid.getNext(), 1, &topic);
-    int rc = sendPacket(len, atimer.left_ms()); // send the subscribe packet
-	if (rc != len) 
-		goto exit; // there was a problem
+    int rc = MQTTSerialize_unsubscribe(buf, limits.MAX_MQTT_PACKET_SIZE, 0, packetid.getNext(), 1, &topic);
+    if (rc <= 0)
+        goto exit;
+    len = rc;
+    if ((rc = sendPacket(len, timer)) != len) // send the subscribe packet
+        goto exit; // there was a problem
     
-    /* wait for unsuback */
-    if (resultHandler == 0)
+    if (waitfor(UNSUBACK, timer) == UNSUBACK)
     {
-        // this will block
-        if (waitfor(UNSUBACK) == UNSUBACK)
-        {
-            int mypacketid;
-            if (MQTTDeserialize_unsuback(&mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-                rc = 0; 
-        }
-    }
-    else
-    {
-        // set unsubscribe response callback function
-        
+        int mypacketid;  // should be the same as the packetid above
+        if (MQTTDeserialize_unsuback(&mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+            rc = 0; 
     }
     
 exit:
@@ -531,50 +503,38 @@
 
 
    
-template<class Network, class Timer, class Thread, class Mutex> int MQTT::Client<Network, Timer, Thread, Mutex>::publish(const char* topicName, Message* message, resultHandler resultHandler)
-{
-	int index = 0;
-	if (this->thread)
-		index = findFreeOperation();	
-	Timer& atimer = operations[index].timer;
-
-	atimer.countdown(limits.command_timeout);
-    MQTTString topic = {(char*)topicName, 0, 0};
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::publish(const char* topicName, Message* message)
+{
+    Timer timer = Timer(limits.command_timeout_ms);
+    
+    MQTTString topicString = {(char*)topicName, 0, 0};
 
-	message->id = packetid.getNext();
+    if (message->qos == QOS1 || message->qos == QOS2)
+        message->id = packetid.getNext();
     
-	int len = MQTTSerialize_publish(buf, limits.MAX_MQTT_PACKET_SIZE, 0, message->qos, message->retained, message->id, topic, (char*)message->payload, message->payloadlen);
-    int rc = sendPacket(len, atimer.left_ms()); // send the subscribe packet
-	if (rc != len) 
-		goto exit; // there was a problem
+    int len = MQTTSerialize_publish(buf, limits.MAX_MQTT_PACKET_SIZE, 0, message->qos, message->retained, message->id, 
+              topicString, (char*)message->payload, message->payloadlen);
+    int rc = sendPacket(len, timer); // send the subscribe packet
+    if (rc != len) 
+        goto exit; // there was a problem
     
-    /* wait for acks */
-    if (resultHandler == 0)
+    if (message->qos == QOS1)
     {
- 		if (message->qos == QOS1)
-		{
-	        if (waitfor(PUBACK, atimer) == PUBACK)
-    	    {
-    	        int type, dup, mypacketid;
-    	        if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-    	            rc = 0; 
-    	    }
-		}
-		else if (message->qos == QOS2)
-		{
-	        if (waitfor(PUBCOMP, atimer) == PUBCOMP)
-	   	    {
-	   	    	int type, dup, mypacketid;
-            	if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
-    	           	rc = 0; 
-			}
-
-		}
+        if (waitfor(PUBACK, timer) == PUBACK)
+        {
+            int type, dup, mypacketid;
+            if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+                rc = 0; 
+        }
     }
-    else
+    else if (message->qos == QOS2)
     {
-        // set publish response callback function
-        
+        if (waitfor(PUBCOMP, timer) == PUBCOMP)
+        {
+            int type, dup, mypacketid;
+            if (MQTTDeserialize_ack(&type, &dup, &mypacketid, readbuf, limits.MAX_MQTT_PACKET_SIZE) == 1)
+                rc = 0; 
+        }
     }
     
 exit:
@@ -582,4 +542,14 @@
 }
 
 
-#endif
+template<class Network, class Timer> int MQTT::Client<Network, Timer>::disconnect()
+{  
+    Timer timer = Timer(limits.command_timeout_ms);     // we might wait for incomplete incoming publishes to complete
+    int len = MQTTSerialize_disconnect(buf, limits.MAX_MQTT_PACKET_SIZE);
+    int rc = sendPacket(len, timer);   // send the disconnect packet
+    
+    return rc;
+}
+
+
+#endif
\ No newline at end of file
--- a/MQTTPacket.lib	Mon Apr 14 21:58:58 2014 +0100
+++ b/MQTTPacket.lib	Mon Apr 28 16:07:51 2014 +0000
@@ -1,1 +1,1 @@
-http://mbed.org/teams/mqtt/code/MQTTPacket/#eea71419676a
+http://mbed.org/teams/mqtt/code/MQTTPacket/#1b8fb13fc6ef