[fixes] Timeout and broker to broker modifications

README.md

@@ -24,6 +24,7 @@ TinyMqtt is a small, fast and capable Mqtt Broker and Client for Esp8266 / Esp32
 
 ## Features
 
+- Async Wifi compatible (me-no-dev/ESPAsyncTCP@^1.2.2)
 - Very fast broker I saw it re-sent 1000 topics per second for two
   clients that had subscribed (payload ~15 bytes ESP8266). No topic lost.
   The max I've seen was 2k msg/s (1 client 1 subscription)

bump_version.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+current_version=$(git describe --tags --abbrev=0)
+if [ "$1" == "-d" ]; then
+  do=0
+  shift
+else
+  do=1
+fi
+if [ "$1" == "" ]; then
+	echo
+	echo "Syntax: $0 [-d] {new_version}"
+	echo
+	echo "  -d : dry run, generate json and update properties but do not run git commands"
+	echo ""
+	echo "  Current version: $current_version"
+	echo
+else
+	echo "Current version: ($current_version)"
+	echo "New version    : ($1)"
+	echo -n "Do you want to proceed ? "
+	read a
+	if [ "$a" == "y" ]; then
+		echo "Doing this..."
+		grep $current_version library.properties
+		if [ "$?" == "0" ]; then
+			sed -i "s/$current_version/$1/" library.properties
+
+      cp library.json.skeleton library.json
+      while ifs= read -r line; do
+        name=$(echo "$line" | sed "s/=.*//g")
+        value=$(echo "$line" | cut -d= -f 2 | sed 's/"//g')
+        echo "  Replacing $name in json"
+        if [ "$name" == "depends" ]; then
+          depends=$(echo "$value" | sed "s/,/ /g")
+          echo "  Depends=$depends"
+        fi
+        echo "  " sed -i "s@#$name@$value@g" library.json
+        sed -i "s@#$name@$value@g" library.json
+      done < library.properties
+      deps=""
+      for depend in $depends; do
+        if [ "$deps" != "" ]; then
+          deps="$deps, "
+        fi
+        deps="$deps'$depend' : '*'"
+      done
+      sed -i "s@#dependencies@$deps@g" library.json
+      sed -i "s/'/\"/g" library.json
+      if [ "$do" == "1" ]; then
+        git tag $1
+        git add library.properties
+        git add library.json
+        git commit -m "Release $1"
+        git push
+        git push --tags
+      fi
+		else
+			echo "Current version does not match library.property version, aborting"
+		fi
+	fi
+fi

examples/tinymqtt-test/tinymqtt-test.ino

@@ -15,8 +15,6 @@
 #include <string>
 #include <map>
 
-using string = TinyString;
-
 bool echo_on = true;
 auto green = TinyConsole::green;
 auto red = TinyConsole::red;
@@ -28,8 +26,11 @@ auto save_cursor = TinyConsole::save_cursor;
 auto restore_cursor = TinyConsole::restore_cursor;
 auto erase_to_end = TinyConsole::erase_to_end;
 
-const char* ssid = "";
+const char *ssid = "Freebox-786A2F";
-const char* password = "";
+const char *password = "usurpavi8dalum64lumine?";
+
+void onCommand(const string &command);
+void eval(string &cmd);
 
 struct free_broker
 {
@@ -43,8 +44,7 @@ struct free_broker
 const std::map<string, free_broker> list =
     {
         {"mqtthq", {"public.mqtthq.com", 8083, "publish/subscribe"}},
-  { "hivemq", { "broker.hivemq.com", 1883, "" }}
+        {"hivemq", {"broker.hivemq.com", 1883, ""}}};
-};
 
 /** Very complex example
  * Console allowing to make any kind of test,
@@ -88,7 +88,8 @@ void setup()
   delay(500);
 
   Console.cls();
-  Console << endl << endl;
+  Console << endl
+          << endl;
   Console << yellow
           << "***************************************************************" << endl;
   Console << "*  Welcome to the TinyMqtt console" << endl;
@@ -99,7 +100,8 @@ void setup()
   if (strlen(ssid) == 0)
     Console << red << "*  ERROR: You must modify ssid/password in order" << endl
             << "          to be able to connect to your Wifi network." << endl;
-  Console << endl << white;
+  Console << endl
+          << white;
 
   Console << "Connecting to '" << ssid << "' ";
 
@@ -109,9 +111,13 @@ void setup()
   WiFi.begin(ssid, password);
 
   while (WiFi.status() != WL_CONNECTED)
-  { Console << '-'; delay(500); }
+  {
+    Console << '-';
+    delay(500);
+  }
 
-  Console << endl << "Connected to " << ssid << "IP address: " << WiFi.localIP() << endl;
+  Console << endl
+          << "Connected to " << ssid << "IP address: " << WiFi.localIP() << endl;
 
   const char *name = "tinytest";
   Console << "Starting MDNS, name= " << name;
@@ -120,12 +126,14 @@ void setup()
   else
     Console << " ok." << endl;
 
-
   MqttBroker *broker = new MqttBroker(1883);
   broker->begin();
   brokers["broker"] = broker;
 
-  if (Console.isTerm()) onCommand("every 333 view");
+  if (Console.isTerm())
+    onCommand("every 333 view");
+
+  Console.prompt();
 }
 
 string getword(string &str, const char *if_empty = nullptr, char sep = ' ');
@@ -137,8 +145,10 @@ int getint(string& str, const int if_empty=0)
   if (sword[0] and isdigit(sword[0]))
   {
     int ret = atoi(sword.c_str());
-    while(isdigit(sword[0]) or sword[0]==' ') sword.erase(0,1);
+    while (isdigit(sword[0]) or sword[0] == ' ')
-    if (sword.length()) str = sword+' '+str;
+      sword.erase(0, 1);
+    if (sword.length())
+      str = sword + ' ' + str;
     return ret;
   }
   str = str2;
@@ -148,7 +158,8 @@ int getint(string& str, const int if_empty=0)
 string getword(string &str, const char *if_empty /*=nullptr*/, char sep /*=' '*/)
 {
   char quote = (str[0] == '"' or str[0] == '\'' ? str[0] : 0);
-  if (quote) str.erase(0,1);
+  if (quote)
+    str.erase(0, 1);
   string sword;
   while (str.length() and (str[0] != sep or quote))
   {
@@ -160,8 +171,10 @@ string getword(string& str, const char* if_empty/*=nullptr*/, char sep/*=' '*/)
     sword += str[0];
     str.erase(0, 1);
   }
-  while(str[0]==sep) str.erase(0,1);
+  while (str[0] == sep)
-  if (if_empty and sword.length()==0) return if_empty;
+    str.erase(0, 1);
+  if (if_empty and sword.length() == 0)
+    return if_empty;
   if (quote == false and sword.length() >= 4 and sword.substr(0, 3) == "rnd")
   {
     sword.erase(0, 3);
@@ -174,7 +187,8 @@ string getword(string& str, const char* if_empty/*=nullptr*/, char sep/*=' '*/)
       {
         sword.erase(0, 1);
         to = getint(sword);
-        if (sword[0]!=')') Console << "Missing ')'" << endl;
+        if (sword[0] != ')')
+          Console << "Missing ')'" << endl;
       }
       else
       {
@@ -188,15 +202,18 @@ string getword(string& str, const char* if_empty/*=nullptr*/, char sep/*=' '*/)
       Console << "Missing '('" << endl;
     }
   }
-  while(str[0]==' ') str.erase(0,1);
+  while (str[0] == ' ')
+    str.erase(0, 1);
   return sword;
 }
 
 bool isaddr(string s)
 {
-  if (s.length()==0 or s.length()>3) return false;
+  if (s.length() == 0 or s.length() > 3)
+    return false;
   for (char c : s)
-    if (c<'0' or c>'9') return false;
+    if (c < '0' or c > '9')
+      return false;
   return true;
 }
 
@@ -225,7 +242,8 @@ string getip(string& str, const char* if_empty=nullptr, char sep=' ')
   }
   for (string s : build)
   {
-    if (addr.length()) addr += '.';
+    if (addr.length())
+      addr += '.';
     addr += s;
   }
   Console << "connect address: " << addr << endl;
@@ -238,20 +256,22 @@ std::set<string> commands = {
     "broker", "blink", "client", "connect",
     "create", "delete", "debug", "help", "interval",
     "list", "ls", "ip", "off", "on", "set",
-  "publish", "reset", "subscribe", "unsubscribe", "view", "echo", "every"
+    "publish", "reset", "subscribe", "unsubscribe", "view", "echo", "every"};
-};
 
 void convertToCommand(string &search)
 {
-  while(search[0]==' ') search.erase(0,1);
+  while (search[0] == ' ')
-  if (search.length()==0) return;
+    search.erase(0, 1);
+  if (search.length() == 0)
+    return;
   string matches;
   int count = 0;
   for (string cmd : commands)
   {
     if (cmd.substr(0, search.length()) == search)
     {
-      if (count) matches +=", ";
+      if (count)
+        matches += ", ";
       count++;
       matches += cmd;
     }
@@ -295,7 +315,6 @@ void replaceVars(string& cmd)
   }
   cmd.erase(0, cmd.find_first_not_of(' '));
   cmd.erase(cmd.find_last_not_of(' ') + 1);
-
 }
 
 bool compare(string s, const char *cmd)
@@ -303,8 +322,10 @@ bool compare(string s, const char* cmd)
   uint8_t p = 0;
   while (s[p++] == *cmd++)
   {
-    if (*cmd==0 or s[p]==0) return true;
+    if (*cmd == 0 or s[p] == 0)
-    if (s[p]==' ') return true;
+      return true;
+    if (s[p] == ' ')
+      return true;
   }
   return false;
 }
@@ -347,10 +368,10 @@ void onCommand(const string& command)
 {
   Console << endl;
   string cmd = command;
-  if (cmd.substr(0,3)!="set") replaceVars(cmd);
+  if (cmd.substr(0, 3) != "set")
+    replaceVars(cmd);
   eval(cmd);
   Console << endl;
-  Console.prompt();
 }
 
 void clientConnect(MqttClient *client, string &cmd)
@@ -406,9 +427,11 @@ void eval(string& cmd)
     }
 
     s = getword(cmd);
-    if (s.length()) convertToCommand(s);
+    if (s.length())
+      convertToCommand(s);
     if (s.length() == 0)
-    {}
+    {
+    }
     else if (compare(s, "debug"))
     {
 #if TINY_MQTT_DEBUG
@@ -445,7 +468,8 @@ void eval(string& cmd)
       {
         for (auto it : clients)
         {
-          if (it.second != client) continue;
+          if (it.second != client)
+            continue;
           Console << "deleted" << endl;
           delete (it.second);
           clients.erase(it.first);
@@ -457,7 +481,8 @@ void eval(string& cmd)
       {
         for (auto it : brokers)
         {
-          if (broker != it.second) continue;
+          if (broker != it.second)
+            continue;
           Console << "deleted" << endl;
           delete (it.second);
           brokers.erase(it.first);
@@ -677,7 +702,8 @@ void eval(string& cmd)
         if (s == "" or brokers.find(s) != brokers.end() or list.find(s) != list.end())
         {
           MqttBroker *broker = nullptr;
-          if (s.length()) broker = brokers[s];
+          if (s.length())
+            broker = brokers[s];
           MqttClient *client = new MqttClient(broker, id);
           clients[id] = client;
           client->setCallback(onPublish);
@@ -790,7 +816,8 @@ void eval(string& cmd)
     }
     else
     {
-      while(s[0]==' ') s.erase(0,1);
+      while (s[0] == ' ')
+        s.erase(0, 1);
       if (s.length())
         Console << "Unknown command (" << s.c_str() << ")" << endl;
     }
@@ -811,7 +838,8 @@ void loop()
 
   for (auto &every : everies)
   {
-    if (not every.active) continue;
+    if (not every.active)
+      continue;
     if (every.ms && every.cmd.length() && ms > every.next)
     {
       string cmd(every.cmd);
@@ -821,6 +849,7 @@ void loop()
       {
         every.next += every.ms;
         Console << yellow << "Underrun every #" << e << ", " << (ms - every.next) << "ms late" << endl;
+        Console.fg(white);
         every.underrun = ms + 5000;
       }
     }

library.json

@@ -0,0 +1,20 @@
+{
+    "name": "TinyMqtt",
+    "keywords": "ethernet, mqtt, m2m, iot",
+    "description": "MQTT is a lightweight messaging protocol. This library allows to host a broker or to use a mqtt client in your ESP 8266 or 32 WROOM. It does support MQTT 3.1.1 with QoS",
+    "repository": {
+        "type": "git",
+        "url": "https://github.com/hsaturn/TinyMqtt.git"
+    },
+    "dependencies":
+    { "hsaturn/TinyConsole" : "*" },
+    "version": "0.9.19",
+    "exclude": "",
+    "examples": "examples/*/*.ino",
+    "frameworks": "arduino",
+    "platforms": [
+        "atmelavr",
+        "espressif8266",
+        "espressif32"
+    ]
+}

library.json.skeleton

@@ -0,0 +1,20 @@
+{
+    "name": "#name",
+    "keywords": "ethernet, mqtt, m2m, iot",
+    "description": "#paragraph",
+    "repository": {
+        "type": "git",
+        "url": "https://github.com/hsaturn/TinyMqtt.git"
+    },
+    "dependencies":
+    { #dependencies },
+    "version": "#version",
+    "exclude": "",
+    "examples": "examples/*/*.ino",
+    "frameworks": "arduino",
+    "platforms": [
+        "atmelavr",
+        "espressif8266",
+        "espressif32"
+    ]
+}

library.properties

@@ -1,5 +1,5 @@
 name=TinyMqtt
-version=0.9.12
+version=0.9.19
 author=Francois BIOT, HSaturn, <hsaturn@gmail.com>
 maintainer=Francois BIOT <hsaturn@gmail.com>
 sentence=A tiny broker and client library for MQTT messaging.
@@ -7,5 +7,5 @@ paragraph=MQTT is a lightweight messaging protocol. This library allows to host
 category=Communication
 url=https://github.com/hsaturn/TinyMqtt
 architectures=*
-depends=TinyConsole
+depends=hsaturn/TinyConsole
 includes=TinyMqtt.h

src/StringIndexer.h

@@ -107,6 +107,8 @@ class IndexedString
       index = source.index;
     }
 
+    IndexedString(IndexedString&& i) : index(i.index) {}
+
     IndexedString(const char* str, uint8_t len)
     {
       index=StringIndexer::strToIndex(str, len);

src/TinyMqtt.cpp

@@ -15,8 +15,10 @@ int TinyMqtt::debug=2;
   std::map<MqttMessage::Type, int> MqttClient::counters;
 #endif
 
-MqttBroker::MqttBroker(uint16_t port)
+MqttBroker::MqttBroker(uint16_t port, uint8_t max_retain_size)
 {
+  debug("New broker" << port);
+  retain_size = max_retain_size;
   server = new TcpServer(port);
 #ifdef TINY_MQTT_ASYNC
   server->onClient(onClient, this);
@@ -116,7 +118,7 @@ void MqttClient::connect(string broker, uint16_t port, uint16_t ka)
 #ifdef TINY_MQTT_ASYNC
   tcp_client->onData(onData, this);
   tcp_client->onConnect(onConnect, this);
-  tcp_client->connect(broker.c_str(), port, ka);
+  tcp_client->connect(broker.c_str(), port);
 #else
   if (tcp_client->connect(broker.c_str(), port))
   {
@@ -142,6 +144,7 @@ void MqttBroker::connect(const string& host, uint16_t port)
   if (remote_broker == nullptr) remote_broker = new MqttClient;
   remote_broker->connect(host, port);
   remote_broker->local_broker = this;  // Because connect removed the link
+  // TODO shouldn't we resubscribe to all client subscriptions ?
 }
 
 void MqttBroker::removeClient(MqttClient* remove)
@@ -211,9 +214,19 @@ void MqttBroker::loop()
   }
 }
 
-MqttError MqttBroker::subscribe(const Topic& topic, uint8_t qos)
+// Obvioulsy called when the broker is connected to another broker.
+MqttError MqttBroker::subscribe(MqttClient* client, const Topic& topic, uint8_t qos)
 {
-  debug("MqttBroker::subscribe");
+  debug("MqttBroker::subscribe to " << topic.str() << ", retained=" << retained.size() );
+  for(auto& [retained_topic, retain]: retained)
+  {
+    debug("  retained: " << retained_topic.str());
+    if (topic.matches(retained_topic))
+    {
+      debug("  -> sending");
+      client->publishIfSubscribed(retained_topic, retain.msg);
+    }
+  }
   if (remote_broker && remote_broker->connected())
   {
     return remote_broker->subscribe(topic, qos);
@@ -221,10 +234,12 @@ MqttError MqttBroker::subscribe(const Topic& topic, uint8_t qos)
   return MqttNowhereToSend;
 }
 
-MqttError MqttBroker::publish(const MqttClient* source, const Topic& topic, MqttMessage& msg) const
+MqttError MqttBroker::publish(const MqttClient* source, const Topic& topic, MqttMessage& msg)
 {
   MqttError retval = MqttOk;
 
+  retain(topic, msg);
+
   debug("MqttBroker::publish");
   int i=0;
   for(auto client: clients)
@@ -294,25 +309,26 @@ void MqttClient::clientAlive(uint32_t more_seconds)
 
 void MqttClient::loop()
 {
-  if (keep_alive && (millis() >= alive))
+  if (keep_alive && (millis() >= alive - 5000))
   {
-    if (local_broker)
+    if (tcp_client && tcp_client->connected())
-    {
-      debug(red << "timeout client");
-      close();
-      debug(red << "closed");
-    }
-    else if (tcp_client && tcp_client->connected())
     {
       debug("pingreq");
-      uint16_t pingreq = MqttMessage::Type::PingReq;
+      static MqttMessage pingreq(MqttMessage::Type::PingReq);
-      tcp_client->write((const char*)(&pingreq), 2);
+      pingreq.sendTo(this);
       clientAlive(0);
 
       // TODO when many MqttClient passes through a local broker
       // there is no need to send one PingReq per instance.
     }
+    else if (local_broker)
+    {
+      debug(red << "timeout client");
+      close();
+      debug(red << "closed");
     }
+  }
+
 #ifndef TINY_MQTT_ASYNC
   while(tcp_client && tcp_client->available()>0)
   {
@@ -391,13 +407,13 @@ MqttError MqttClient::subscribe(Topic topic, uint8_t qos)
 
   subscriptions.insert(topic);
 
-  if (local_broker==nullptr) // remote broker
+  if (local_broker==nullptr) // connected to a remote broker
   {
     return sendTopic(topic, MqttMessage::Type::Subscribe, qos);
   }
   else
   {
-    return local_broker->subscribe(topic, qos);
+    return local_broker->subscribe(this, topic, qos);
   }
   return ret;
 }
@@ -568,7 +584,7 @@ void MqttClient::processMessage(MqttMessage* mesg)
             }
             else
               qoss.push_back(qos);
-            subscriptions.insert(topic);
+            subscribe(topic);
           }
           else
           {
@@ -618,8 +634,8 @@ void MqttClient::processMessage(MqttMessage* mesg)
           #if TINY_MQTT_DEBUG
             if (TinyMqtt::debug >= 2)
             {
-              Console << (isSubscribedTo(published) ? "not" : "") << " subscribed.\n";
+              Console << (isSubscribedTo(published) ? "not" : "") << " subscribed.\r\n";
-              Console << "has " << (callback ? "" : "no ") << " callback.\n";
+              Console << "has " << (callback ? "" : "no ") << " callback.\r\n";
             }
           #endif
           if (callback and isSubscribedTo(published))
@@ -728,9 +744,9 @@ bool Topic::matches(const Topic& topic) const
 
 
 // publish from local client
-MqttError MqttClient::publish(const Topic& topic, const char* payload, size_t pay_length)
+MqttError MqttClient::publish(const Topic& topic, const char* payload, size_t pay_length, bool retain)
 {
-  MqttMessage msg(MqttMessage::Publish);
+  MqttMessage msg(MqttMessage::Publish, retain ? 1 : 0);
   msg.add(topic);
   msg.add(payload, pay_length, false);
   msg.complete();
@@ -894,6 +910,35 @@ MqttError MqttMessage::sendTo(MqttClient* client)
   return MqttOk;
 }
 
+void MqttBroker::retainDrop()
+{
+  if (retained.size() >= retain_size)
+  {
+    std::map<Topic, Retain>::iterator oldest = retained.begin();
+    auto it = oldest;
+    while(++it != retained.end())
+    {
+      if (oldest->second.timestamp > it->second.timestamp)
+        oldest = it;
+    }
+    retained.erase(oldest);
+  }
+}
+
+void MqttBroker::retain(const Topic& topic, const MqttMessage& msg)
+{
+  debug("MqttBroker::retain msg_type=" << _HEX(msg.type()));
+  if (retain_size==0 or msg.type() != MqttMessage::Publish) return;
+  if (msg.flags() & 1)  // flag RETAIN
+  {
+    debug("  retaining " << topic.str());
+    if (retained.find(topic) == retained.end()) retainDrop();
+    // FIXME if payload size == 0 remove message from retained
+    Retain r(micros(), msg);
+    retained.insert({ topic, std::move(r)});
+  }
+}
+
 void MqttMessage::hexdump(const char* prefix) const
 {
   (void)prefix;

src/TinyMqtt.h

@@ -121,7 +121,10 @@ class MqttMessage
       return (*bun << 8) | bun[1]; }
 
     MqttMessage() { reset(); }
-    MqttMessage(Type t, uint8_t bits_d3_d0=0) { create(t); buffer[0] |= bits_d3_d0; }
+    MqttMessage(Type t, uint8_t bits_d3_d0=0) { create(t); buffer[0] |= (bits_d3_d0 & 0xF); }
+    MqttMessage(const MqttMessage& m)
+      : buffer(m.buffer), vheader(m.vheader), size(m.size), state(m.state) {}
+
     void incoming(char byte);
     void add(char byte) { incoming(byte); }
     void add(const char* p, size_t len, bool addLength=true );
@@ -156,6 +159,15 @@ class MqttMessage
     MqttError sendTo(MqttClient*);
     void hexdump(const char* prefix=nullptr) const;
 
+    MqttMessage& operator = (MqttMessage&& m)
+    {
+      buffer = std::move(m.buffer);
+      vheader = m.vheader;
+      size = m.size;
+      state = m.state;
+      return *this;
+    }
+
   private:
     void encodeLength();
 
@@ -228,11 +240,11 @@ class MqttClient
     };
 
     // Publish from client to the world
-    MqttError publish(const Topic&, const char* payload, size_t pay_length);
+    MqttError publish(const Topic&, const char* payload, size_t pay_length, bool retain=false);
-    MqttError publish(const Topic& t, const char* payload) { return publish(t, payload, strlen(payload)); }
+    MqttError publish(const Topic& t, const char* payload, bool retain=false) { return publish(t, payload, strlen(payload), retain); }
-    MqttError publish(const Topic& t, const String& s) { return publish(t, s.c_str(), s.length()); }
+    MqttError publish(const Topic& t, const String& s, bool retain=false) { return publish(t, s.c_str(), s.length(), retain); }
-    MqttError publish(const Topic& t, const string& s) { return publish(t,s.c_str(),s.length());}
+    MqttError publish(const Topic& t, const string& s, bool retain=false) { return publish(t,s.c_str(),s.length(), retain);}
-    MqttError publish(const Topic& t) { return publish(t, nullptr, 0);};
+    MqttError publish(const Topic& t, bool retain=false) { return publish(t, nullptr, 0, retain);};
 
     MqttError subscribe(Topic topic, uint8_t qos=0);
     MqttError unsubscribe(Topic topic);
@@ -317,15 +329,9 @@ class MqttClient
 
 class MqttBroker
 {
-  enum __attribute__((packed)) State
-  {
-    Disconnected,  // Also the initial state
-    Connecting,    // connect and sends a fake publish to avoid circular cnx
-    Connected,     // this->broker is connected and circular cnx avoided
-  };
   public:
     // TODO limit max number of clients
-    MqttBroker(uint16_t port);
+    MqttBroker(uint16_t port, uint8_t retain_size=0);
     ~MqttBroker();
 
     void begin() { server->begin(); }
@@ -334,9 +340,10 @@ class MqttBroker
     /** Connect the broker to a parent broker */
     void connect(const string& host, uint16_t port=1883);
     /** returns true if connected to another broker */
-    bool connected() const { return state == Connected; }
+    bool connected() const { return remote_broker ? remote_broker->connected() : false; }
 
     size_t clientsCount() const { return clients.size(); }
+    void retain(uint8_t size) { retain_size = size; }
 
     void dump(string indent="")
     {
@@ -356,10 +363,9 @@ class MqttBroker
     bool checkPassword(const char* password, uint8_t len) const
     { return compareString(auth_password, password, len); }
 
+    MqttError publish(const MqttClient* source, const Topic& topic, MqttMessage& msg);
 
-    MqttError publish(const MqttClient* source, const Topic& topic, MqttMessage& msg) const;
+    MqttError subscribe(MqttClient*, const Topic& topic, uint8_t qos);
-
-    MqttError subscribe(const Topic& topic, uint8_t qos);
 
     // For clients that are added not by the broker itself (local clients)
     void addClient(MqttClient* client);
@@ -375,5 +381,25 @@ class MqttBroker
     const char* auth_password = "guest";
     MqttClient* remote_broker = nullptr;
 
-    State state = Disconnected;
+    void retain(const Topic& topic, const MqttMessage& msg);
+    void retainDrop();
+
+    struct Retain
+    {
+      Retain(unsigned long ts, const MqttMessage& m) : timestamp(ts), msg(m) {}
+      Retain(Retain&& r) : timestamp(r.timestamp), msg(std::move(r.msg)) {}
+
+      Retain& operator=(Retain&& r)
+      {
+        timestamp = r.timestamp;
+        msg = std::move(r.msg);
+        return *this;
+      }
+
+      unsigned long timestamp;
+      MqttMessage msg;
+    };
+
+    std::map<Topic, Retain> retained;
+    uint8_t retain_size;
 };