diff --git a/api/js/jsapi/egw.js b/api/js/jsapi/egw.js
index f1d3e5f597..5c3592e9cb 100644
--- a/api/js/jsapi/egw.js
+++ b/api/js/jsapi/egw.js
@@ -415,7 +415,8 @@
 				{
 					egw.json('websocket', {}, undefined, this).openWebSocket(
 						egw_script.getAttribute('data-websocket-url'),
-						JSON.parse(egw_script.getAttribute('data-websocket-tokens'))
+						JSON.parse(egw_script.getAttribute('data-websocket-tokens')),
+						parseInt(egw_script.getAttribute('data-websocket-account_id'))
 					);
 				}
 			}
diff --git a/api/js/jsapi/egw_global.d.ts b/api/js/jsapi/egw_global.d.ts
index e199a28468..db2c3d5ae1 100644
--- a/api/js/jsapi/egw_global.d.ts
+++ b/api/js/jsapi/egw_global.d.ts
@@ -685,11 +685,12 @@ declare class JsonRequest
 	 * Open websocket to push server (and keeps it open)
 	 *
 	 * @param {string} url this.websocket(s)://host:port
-	 * @param {array} tokens tokens to subscribe too
+	 * @param {array} tokens tokens to subscribe too: sesssion-, user- and instance-token (in that order!)
+	 * @param {number} account_id to connect for
 	 * @param {function} error option error callback(_msg) used instead our default this.error
 	 * @param {int} reconnect timeout in ms (internal)
 	 */
-	openWebSocket(url : string, tokens : string[], error : Function, reconnect : number);
+	openWebSocket(url : string, tokens : string[], account_id : number, error : Function, reconnect : number);
 }
 
 /**
diff --git a/api/js/jsapi/egw_json.js b/api/js/jsapi/egw_json.js
index 4e1b843f26..5ef159af12 100644
--- a/api/js/jsapi/egw_json.js
+++ b/api/js/jsapi/egw_json.js
@@ -98,11 +98,12 @@ egw.extend('json', egw.MODULE_WND_LOCAL, function(_app, _wnd)
 	 * Open websocket to push server (and keeps it open)
 	 *
 	 * @param {string} url this.websocket(s)://host:port
-	 * @param {array} tokens tokens to subscribe too
+	 * @param {array} tokens tokens to subscribe too: sesssion-, user- and instance-token (in that order!)
+	 * @param {number} account_id to connect for
 	 * @param {function} error option error callback(_msg) used instead our default this.error
 	 * @param {int} reconnect timeout in ms (internal)
 	 */
-	json_request.prototype.openWebSocket = function(url, tokens, error, reconnect)
+	json_request.prototype.openWebSocket = function(url, tokens, account_id, error, reconnect)
 	{
 		const min_reconnect_time = 1000;
 		const max_reconnect_time = 300000;
@@ -113,7 +114,8 @@ egw.extend('json', egw.MODULE_WND_LOCAL, function(_app, _wnd)
 		{
 			reconnect_time = min_reconnect_time;
 			this.websocket.send(JSON.stringify({
-				subscribe: tokens
+				subscribe: tokens,
+				account_id: parseInt(account_id)
 			}));
 		}, this);
 
@@ -147,7 +149,7 @@ egw.extend('json', egw.MODULE_WND_LOCAL, function(_app, _wnd)
 				// e.g. server process killed or network down
 				// event.code is usually 1006 in this case
 				console.log('[close] Connection died --> reconnect in '+reconnect_time+'ms');
-				window.setTimeout(jQuery.proxy(this.openWebSocket, this, url, tokens, error, reconnect_time), reconnect_time);
+				window.setTimeout(jQuery.proxy(this.openWebSocket, this, url, tokens, account_id, error, reconnect_time), reconnect_time);
 			}
 		}, this);
 	},
diff --git a/api/src/Json/Push.php b/api/src/Json/Push.php
index 277afe991c..cad34d2f19 100644
--- a/api/src/Json/Push.php
+++ b/api/src/Json/Push.php
@@ -49,6 +49,18 @@ class Push extends Msg
 	 */
 	const SESSION = null;
 
+	/**
+	 * How long to cache online status / maximum frequency for querying
+	 */
+	const INSTANCE_ONLINE_CACHE_EXPIRATION = 10;
+
+	/**
+	 * account_id's of users currently online
+	 *
+	 * @var array|null
+	 */
+	protected static $online;
+
 	/**
 	 *
 	 * @param int $account_id =null account_id to push message too or
@@ -67,6 +79,37 @@ class Push extends Msg
 	 * @throws Exception\NotOnline if $account_id is not online
 	 */
 	protected function addGeneric($key, $data)
+	{
+		self::checkSetBackend();
+
+		self::$backend->addGeneric($this->account_id, $key, $data);
+	}
+
+	/**
+	 * Get users online / connected to push-server
+	 *
+	 * @return array of integer account_id currently available for push
+	 */
+	public function online()
+	{
+		if (!isset(self::$online))
+		{
+			self::$online = Api\Cache::getInstance(__CLASS__, 'online', function()
+			{
+				self::checkSetBackend();
+
+				return self::$backend->online();
+			}, [], self::INSTANCE_ONLINE_CACHE_EXPIRATION);
+		}
+		return self::$online;
+	}
+
+	/**
+	 * Check and if neccessary set push backend
+	 *
+	 * @throws Exception\NotOnline
+	 */
+	protected function checkSetBackend()
 	{
 		if (!isset(self::$backend))
 		{
diff --git a/api/src/Json/PushBackend.php b/api/src/Json/PushBackend.php
index 95d139656a..3e6f9402fe 100644
--- a/api/src/Json/PushBackend.php
+++ b/api/src/Json/PushBackend.php
@@ -27,4 +27,11 @@ interface PushBackend
 	 * @throws Exception\NotOnline if $account_id is not online
 	 */
 	public function addGeneric($account_id, $key, $data);
+
+	/**
+	 * Get users online / connected to push-server
+	 *
+	 * @return array of integer account_id currently available for push
+	 */
+	public function online();
 }
diff --git a/notifications/inc/class.notifications_push.inc.php b/notifications/inc/class.notifications_push.inc.php
index 3d9287415f..f7c30226d7 100644
--- a/notifications/inc/class.notifications_push.inc.php
+++ b/notifications/inc/class.notifications_push.inc.php
@@ -135,5 +135,20 @@ class notifications_push implements Json\PushBackend
 	{
 		self::$db =& $GLOBALS['egw']->db;
 	}
+
+	/**
+	 * Get users online / connected to push-server
+	 *
+	 * @return array of integer account_id currently available for push
+	 */
+	public function online()
+	{
+		$online = [];
+		foreach($GLOBALS['egw']->session->session_list(0, 'DESC', 'session_dla', true, ['notification_heartbeat IS NOT NULL']) as $row)
+		{
+			$online[] = (int)$row['account_id'];
+		}
+		return array_unique($online);
+	}
 }
 notifications_push::init_static();