diff --git a/Dockerfile b/Dockerfile
index faff564..3bd181e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -9,6 +9,8 @@ ENV XMR_DEBUG=false
 ENV XMR_QUEUE_POLL=5
 ENV XMR_QUEUE_SIZE=10
 ENV XMR_IPV6PUBSUPPORT=false
+ENV XMR_RELAY_OLD_MESSAGES=false
+ENV XMR_RELAY_MESSAGES=false
 
 RUN apt-get update && apt-get install -y libzmq3-dev git \
     && rm -rf /var/lib/apt/lists/*
diff --git a/composer.json b/composer.json
index 739f8a4..967997a 100644
--- a/composer.json
+++ b/composer.json
@@ -31,7 +31,8 @@
     "react/react": "^1.4",
     "react/socket": "^1.16",
     "react/zmq": "^0.4.0",
-    "cboden/ratchet": "^0.4.4"
+    "cboden/ratchet": "^0.4.4",
+    "guzzlehttp/guzzle": "^7.9"
   },
   "autoload": {
     "psr-4": {
diff --git a/composer.lock b/composer.lock
index 226ad28..3b65780 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "2962bb0981206b9c30166891cdec6983",
+    "content-hash": "58cf90f353cd3f8d2862b0ebb1dff300",
     "packages": [
         {
             "name": "cboden/ratchet",
@@ -172,6 +172,215 @@
             },
             "time": "2020-11-24T22:02:12+00:00"
         },
+        {
+            "name": "guzzlehttp/guzzle",
+            "version": "7.9.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/guzzle/guzzle.git",
+                "reference": "d281ed313b989f213357e3be1a179f02196ac99b"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/guzzle/guzzle/zipball/d281ed313b989f213357e3be1a179f02196ac99b",
+                "reference": "d281ed313b989f213357e3be1a179f02196ac99b",
+                "shasum": ""
+            },
+            "require": {
+                "ext-json": "*",
+                "guzzlehttp/promises": "^1.5.3 || ^2.0.3",
+                "guzzlehttp/psr7": "^2.7.0",
+                "php": "^7.2.5 || ^8.0",
+                "psr/http-client": "^1.0",
+                "symfony/deprecation-contracts": "^2.2 || ^3.0"
+            },
+            "provide": {
+                "psr/http-client-implementation": "1.0"
+            },
+            "require-dev": {
+                "bamarni/composer-bin-plugin": "^1.8.2",
+                "ext-curl": "*",
+                "guzzle/client-integration-tests": "3.0.2",
+                "php-http/message-factory": "^1.1",
+                "phpunit/phpunit": "^8.5.39 || ^9.6.20",
+                "psr/log": "^1.1 || ^2.0 || ^3.0"
+            },
+            "suggest": {
+                "ext-curl": "Required for CURL handler support",
+                "ext-intl": "Required for Internationalized Domain Name (IDN) support",
+                "psr/log": "Required for using the Log middleware"
+            },
+            "type": "library",
+            "extra": {
+                "bamarni-bin": {
+                    "bin-links": true,
+                    "forward-command": false
+                }
+            },
+            "autoload": {
+                "files": [
+                    "src/functions_include.php"
+                ],
+                "psr-4": {
+                    "GuzzleHttp\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Graham Campbell",
+                    "email": "hello@gjcampbell.co.uk",
+                    "homepage": "https://github.com/GrahamCampbell"
+                },
+                {
+                    "name": "Michael Dowling",
+                    "email": "mtdowling@gmail.com",
+                    "homepage": "https://github.com/mtdowling"
+                },
+                {
+                    "name": "Jeremy Lindblom",
+                    "email": "jeremeamia@gmail.com",
+                    "homepage": "https://github.com/jeremeamia"
+                },
+                {
+                    "name": "George Mponos",
+                    "email": "gmponos@gmail.com",
+                    "homepage": "https://github.com/gmponos"
+                },
+                {
+                    "name": "Tobias Nyholm",
+                    "email": "tobias.nyholm@gmail.com",
+                    "homepage": "https://github.com/Nyholm"
+                },
+                {
+                    "name": "Márk Sági-Kazár",
+                    "email": "mark.sagikazar@gmail.com",
+                    "homepage": "https://github.com/sagikazarmark"
+                },
+                {
+                    "name": "Tobias Schultze",
+                    "email": "webmaster@tubo-world.de",
+                    "homepage": "https://github.com/Tobion"
+                }
+            ],
+            "description": "Guzzle is a PHP HTTP client library",
+            "keywords": [
+                "client",
+                "curl",
+                "framework",
+                "http",
+                "http client",
+                "psr-18",
+                "psr-7",
+                "rest",
+                "web service"
+            ],
+            "support": {
+                "issues": "https://github.com/guzzle/guzzle/issues",
+                "source": "https://github.com/guzzle/guzzle/tree/7.9.2"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/GrahamCampbell",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/Nyholm",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/guzzlehttp/guzzle",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2024-07-24T11:22:20+00:00"
+        },
+        {
+            "name": "guzzlehttp/promises",
+            "version": "2.0.4",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/guzzle/promises.git",
+                "reference": "f9c436286ab2892c7db7be8c8da4ef61ccf7b455"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/guzzle/promises/zipball/f9c436286ab2892c7db7be8c8da4ef61ccf7b455",
+                "reference": "f9c436286ab2892c7db7be8c8da4ef61ccf7b455",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.2.5 || ^8.0"
+            },
+            "require-dev": {
+                "bamarni/composer-bin-plugin": "^1.8.2",
+                "phpunit/phpunit": "^8.5.39 || ^9.6.20"
+            },
+            "type": "library",
+            "extra": {
+                "bamarni-bin": {
+                    "bin-links": true,
+                    "forward-command": false
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "GuzzleHttp\\Promise\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Graham Campbell",
+                    "email": "hello@gjcampbell.co.uk",
+                    "homepage": "https://github.com/GrahamCampbell"
+                },
+                {
+                    "name": "Michael Dowling",
+                    "email": "mtdowling@gmail.com",
+                    "homepage": "https://github.com/mtdowling"
+                },
+                {
+                    "name": "Tobias Nyholm",
+                    "email": "tobias.nyholm@gmail.com",
+                    "homepage": "https://github.com/Nyholm"
+                },
+                {
+                    "name": "Tobias Schultze",
+                    "email": "webmaster@tubo-world.de",
+                    "homepage": "https://github.com/Tobion"
+                }
+            ],
+            "description": "Guzzle promises library",
+            "keywords": [
+                "promise"
+            ],
+            "support": {
+                "issues": "https://github.com/guzzle/promises/issues",
+                "source": "https://github.com/guzzle/promises/tree/2.0.4"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/GrahamCampbell",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/Nyholm",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/guzzlehttp/promises",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2024-10-17T10:06:22+00:00"
+        },
         {
             "name": "guzzlehttp/psr7",
             "version": "2.7.0",
@@ -374,6 +583,58 @@
             ],
             "time": "2022-06-09T08:53:42+00:00"
         },
+        {
+            "name": "psr/http-client",
+            "version": "1.0.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/http-client.git",
+                "reference": "bb5906edc1c324c9a05aa0873d40117941e5fa90"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/http-client/zipball/bb5906edc1c324c9a05aa0873d40117941e5fa90",
+                "reference": "bb5906edc1c324c9a05aa0873d40117941e5fa90",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.0 || ^8.0",
+                "psr/http-message": "^1.0 || ^2.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Http\\Client\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "https://www.php-fig.org/"
+                }
+            ],
+            "description": "Common interface for HTTP clients",
+            "homepage": "https://github.com/php-fig/http-client",
+            "keywords": [
+                "http",
+                "http-client",
+                "psr",
+                "psr-18"
+            ],
+            "support": {
+                "source": "https://github.com/php-fig/http-client"
+            },
+            "time": "2023-09-23T14:17:50+00:00"
+        },
         {
             "name": "psr/http-factory",
             "version": "1.1.0",
diff --git a/entrypoint.sh b/entrypoint.sh
index adfeb5b..1d7d085 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -1,5 +1,26 @@
 #!/bin/sh
 
+#
+# Copyright (C) 2024 Xibo Signage Ltd
+#
+# Xibo - Digital Signage - https://xibosignage.com
+#
+# This file is part of Xibo.
+#
+# Xibo is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# any later version.
+#
+# Xibo is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with Xibo.  If not, see <http://www.gnu.org/licenses/>.
+#
+
 # Write config.json
 echo '{' > /opt/xmr/config.json
 echo '  "sockets": {' >> /opt/xmr/config.json
@@ -10,7 +31,9 @@ echo '  },' >> /opt/xmr/config.json
 echo '  "queuePoll": '$XMR_QUEUE_POLL',' >> /opt/xmr/config.json
 echo '  "queueSize": '$XMR_QUEUE_SIZE',' >> /opt/xmr/config.json
 echo '  "debug": '$XMR_DEBUG',' >> /opt/xmr/config.json
-echo '  "ipv6PubSupport": '$XMR_IPV6PUBSUPPORT >> /opt/xmr/config.json
+echo '  "ipv6PubSupport": '$XMR_IPV6PUBSUPPORT',' >> /opt/xmr/config.json
+echo '  "relayOldMessages": '$XMR_RELAY_OLD_MESSAGES',' >> /opt/xmr/config.json
+echo '  "relayMessages": '$XMR_RELAY_MESSAGES >> /opt/xmr/config.json
 echo '}' >> /opt/xmr/config.json
 
 /usr/local/bin/php /opt/xmr/index.php
\ No newline at end of file
diff --git a/index.php b/index.php
index df99b4c..47a81a9 100644
--- a/index.php
+++ b/index.php
@@ -29,6 +29,7 @@
 use React\EventLoop\Loop;
 use React\Http\Message\Response;
 use Xibo\Controller\Api;
+use Xibo\Controller\Relay;
 use Xibo\Controller\Server;
 use Xibo\Entity\Queue;
 
@@ -68,8 +69,15 @@
 $log->pushHandler(new StreamHandler(STDOUT, $logLevel));
 
 // Queue settings
-$queuePoll = (property_exists($config, 'queuePoll')) ? $config->queuePoll : 5;
-$queueSize = (property_exists($config, 'queueSize')) ? $config->queueSize : 10;
+$queuePoll = $config->queuePoll ?? 5;
+$queueSize = $config->queueSize ?? 10;
+
+// Create a client to relay messages
+$relay = new Relay(
+    $log,
+    $config->relayMessages ?? '',
+    $config->relayOldMessages ?? '',
+);
 
 // Create an in memory message queue.
 $messageQueue = new Queue();
@@ -77,37 +85,10 @@
 try {
     $loop = Loop::get();
 
-    // Web Socket server
-    $messagingServer = new Server($messageQueue, $log);
-    $wsSocket = new React\Socket\SocketServer($config->sockets->ws);
-    $wsServer = new WsServer($messagingServer);
-    $ioServer = new IoServer(
-        new HttpServer($wsServer),
-        $wsSocket,
-        $loop
-    );
-
-    // Enable keep alive
-    $wsServer->enableKeepAlive($ioServer->loop);
-
-    $log->info('WS listening on ' . $config->sockets->ws);
-
-    // LEGACY: Pub socket for messages to Players (subs)
-    $publisher = (new React\ZMQ\Context($loop))->getSocket(ZMQ::SOCKET_PUB);
-
-    // Set PUB socket options
-    if (isset($config->ipv6PubSupport) && $config->ipv6PubSupport === true) {
-        $log->debug('Pub MQ Setting socket option for IPv6 to TRUE');
-        $publisher->setSockOpt(\ZMQ::SOCKOPT_IPV6, true);
-    }
-
-    foreach ($config->sockets->zmq as $pubOn) {
-        $log->info(sprintf('Bind to %s for Publish.', $pubOn));
-        $publisher->bind($pubOn);
-    }
-
+    // Private API
+    // -----------
     // Create a private API to receive messages from the CMS
-    $api = new Api($messageQueue, $log);
+    $api = new Api($messageQueue, $log, $relay);
 
     // Create a HTTP server to handle requests to the API
     $http = new React\Http\HttpServer(function (Psr\Http\Message\ServerRequestInterface $request) use ($log, $api) {
@@ -139,9 +120,52 @@
 
     $log->info('HTTP listening');
 
+    // WS
+    // ----
+    // Web Socket server
+    $messagingServer = new Server($messageQueue, $log);
+    $wsSocket = new React\Socket\SocketServer($config->sockets->ws);
+    $wsServer = new WsServer($messagingServer);
+    $ioServer = new IoServer(
+        new HttpServer($wsServer),
+        $wsSocket,
+        $loop
+    );
+
+    // Enable keep alive
+    $wsServer->enableKeepAlive($ioServer->loop);
+
+    $log->info('WS listening on ' . $config->sockets->ws);
+
+    // PUB/SUB
+    // -------
+    // LEGACY: Pub socket for messages to Players (subs)
+    if ($relay->isRelayOld()) {
+        $log->info('Legacy: relaying old messages');
+
+        $publisher = null;
+        $relay->configureZmq();
+    } else {
+        $log->info('Legacy: handling old messages');
+
+        $publisher = (new React\ZMQ\Context($loop))->getSocket(ZMQ::SOCKET_PUB);
+
+        // Set PUB socket options
+        if (isset($config->ipv6PubSupport) && $config->ipv6PubSupport === true) {
+            $log->debug('Pub MQ Setting socket option for IPv6 to TRUE');
+            $publisher->setSockOpt(\ZMQ::SOCKOPT_IPV6, true);
+        }
+
+        foreach ($config->sockets->zmq as $pubOn) {
+            $log->info(sprintf('Bind to %s for Publish.', $pubOn));
+            $publisher->bind($pubOn);
+        }
+    }
+
     // Queue Processor
+    // ---------------
     $log->debug('Adding a queue processor for every ' . $queuePoll . ' seconds');
-    $loop->addPeriodicTimer($queuePoll, function() use ($log, $messagingServer, $publisher, $messageQueue, $queueSize) {
+    $loop->addPeriodicTimer($queuePoll, function() use ($log, $messagingServer, $relay, $publisher, $messageQueue, $queueSize) {
         // Is there work to be done
         if ($messageQueue->hasItems()) {
             $log->debug('Queue Poll - work to be done.');
@@ -167,12 +191,20 @@
                 if ($msg->isWebSocket) {
                     $display = $messagingServer->getDisplayById($msg->channel);
                     if ($display === null) {
-                        $log->info('Display ' . $msg->channel . ' not connected');
-                        continue;
+                        if ($relay->isRelay()) {
+                            $relay->relay($msg);
+                        } else {
+                            $log->info('Display ' . $msg->channel . ' not connected');
+                        }
+                    } else {
+                        $display->connection->send($msg->message);
                     }
-                    $display->connection->send($msg->message);
-                } else {
+                } else if ($relay->isRelayOld()) {
+                    $relay->relay($msg);
+                } else if ($publisher !== null) {
                     $publisher->sendmulti([$msg->channel, $msg->key, $msg->message], \ZMQ::MODE_DONTWAIT);
+                } else {
+                    $log->error('No route to send');
                 }
 
                 $log->debug('Popped ' . $i . ' from the queue, new queue size ' . $messageQueue->queueSize());
@@ -188,7 +220,7 @@
         $messagingServer->heartbeat();
 
         // Send to PUB queue
-        $publisher->sendmulti(["H", "", ""], \ZMQ::MODE_DONTWAIT);
+        $publisher?->sendmulti(["H", "", ""], \ZMQ::MODE_DONTWAIT);
     });
 
     // Key management
diff --git a/src/Controller/Api.php b/src/Controller/Api.php
index 655e955..8aa591e 100644
--- a/src/Controller/Api.php
+++ b/src/Controller/Api.php
@@ -29,7 +29,8 @@ class Api
 {
     public function __construct(
         private readonly Queue $queue,
-        private readonly LoggerInterface $logger
+        private readonly LoggerInterface $logger,
+        private readonly Relay $relay,
     ) {
     }
 
@@ -50,6 +51,11 @@ public function handleMessage(array $message): Response
         } else if ($type === 'keys') {
             // Register new keys for this CMS.
             $this->queue->addKey($message['id'], $message['key']);
+
+            // Relay new keys.
+            if ($this->relay->isRelay()) {
+                $this->relay->relayArray($message);
+            }
         } else if ($type === 'multi') {
             $this->logger->debug('Queuing multiple messages');
             foreach ($message['messages'] as $message) {
diff --git a/src/Controller/Relay.php b/src/Controller/Relay.php
new file mode 100644
index 0000000..59dbb58
--- /dev/null
+++ b/src/Controller/Relay.php
@@ -0,0 +1,128 @@
+<?php
+/*
+ * Copyright (C) 2024 Xibo Signage Ltd
+ *
+ * Xibo - Digital Signage - https://xibosignage.com
+ *
+ * This file is part of Xibo.
+ *
+ * Xibo is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * any later version.
+ *
+ * Xibo is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Xibo.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Xibo\Controller;
+
+
+use GuzzleHttp\Client;
+use GuzzleHttp\Exception\GuzzleException;
+use Psr\Log\LoggerInterface;
+use Xibo\Entity\Message;
+
+class Relay
+{
+    private readonly ?Client $client;
+    private ?\ZMQSocket $socket;
+
+    public function __construct(
+        private readonly LoggerInterface $logger,
+        private readonly string $relayMessages,
+        private string $relayOldMessages,
+    ) {
+        // Create a client for us to use
+        if (!empty($this->relayMessages)) {
+            $this->client = new Client([
+                'base_uri' => $this->relayMessages,
+            ]);
+        } else {
+            $this->client = null;
+        }
+    }
+
+    public function configureZmq(): void
+    {
+        // Create a socket for us to use.
+        try {
+            $this->socket = (new \ZMQContext())->getSocket(\ZMQ::SOCKET_REQ);
+            $this->socket->setSockOpt(\ZMQ::SOCKOPT_LINGER, 2000);
+            $this->socket->connect($this->relayOldMessages);
+        } catch (\Exception $exception) {
+            $this->socket = null;
+            $this->relayOldMessages = null;
+
+            $this->logger->critical('Unable to connect to old message relay: '
+                . $this->relayOldMessages . ', e = ' . $exception->getMessage());
+        }
+    }
+
+    public function isRelay(): bool
+    {
+        return !empty($this->relayMessages);
+    }
+
+    public function isRelayOld(): bool
+    {
+        return !empty($this->relayOldMessages);
+    }
+
+    /**
+     * Relay a message appropriately
+     * @param \Xibo\Entity\Message $message
+     * @return void
+     */
+    public function relay(Message $message): void
+    {
+        if ($message->isWebSocket) {
+            $this->relayArray($message->jsonSerialize());
+        } else {
+            try {
+                $this->socket->send(json_encode($message));
+            } catch (\ZMQSocketException $socketException) {
+                $this->logger->error('relay: [' . $socketException->getCode() . '] ' . $socketException->getMessage());
+                return;
+            }
+
+            $retries = 15;
+
+            do {
+                try {
+                    $reply = $this->socket->recv(\ZMQ::MODE_DONTWAIT);
+
+                    if ($reply !== false) {
+                        break;
+                    }
+                } catch (\ZMQSocketException $socketException) {
+                    $this->logger->error('relay: [' . $socketException->getCode() . '] ' . $socketException->getMessage());
+                    break;
+                }
+
+                usleep(100000);
+            } while (--$retries);
+        }
+    }
+
+    /**
+     * Relay array (only ever a message over private API)
+     * @param array $message
+     * @return void
+     */
+    public function relayArray(array $message): void
+    {
+        try {
+            $this->client?->post('/', [
+                'json' => $message,
+            ]);
+        } catch (GuzzleException | \Exception $e) {
+            $this->logger->error('relayArray: Unable to relay, e = ' . $e->getMessage());
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/Entity/Message.php b/src/Entity/Message.php
index 722e8bd..8f7e26c 100644
--- a/src/Entity/Message.php
+++ b/src/Entity/Message.php
@@ -21,11 +21,22 @@
  */
 namespace Xibo\Entity;
 
-class Message
+class Message implements \JsonSerializable
 {
     public string $channel;
     public string $key;
     public string $message;
     public int $qos;
     public bool $isWebSocket;
+
+    public function jsonSerialize(): array
+    {
+        return [
+            'channel' => $this->channel,
+            'key' => $this->key,
+            'message' => $this->message,
+            'qos' => $this->qos,
+            'isWebSocket' => $this->isWebSocket,
+        ];
+    }
 }