> ## Documentation Index > Fetch the complete documentation index at: https://devdocs.xbox.com/llms.txt > Use this file to discover all available pages before exploring further. # Lobby and Matchmaking real-time messages > How the PlayFab Lobby and Matchmaking SDK delivers real-time PubSub messages for lobby membership, property changes, and matchmaking ticket state updates. ## Overview The Matchmaking and Lobby features have built in support for real-time messages. Sending messages to players about changes to Matchmaking or Lobby has never been easier, as the work to handle messages is done for you in the [PlayFab Lobby and Matchmaking SDK](/services/playfab/multiplayer/lobby/lobby-matchmaking-sdks/lobby-matchmaking-sdks). New APIs will allow connected clients to subscribe for messages about Lobby and Matchmaking changes. With this addition, you'll no longer need to poll for changes to matches or lobbies. The SDK has been designed to simplify your work. The SDK manages calls between game clients or servers and PlayFab Lobby and Matchmaking services. It handles the delivery of messages from those services to connected clients in real time. Real-time messages have cross-platform support, and will work anywhere PlayFab supplies an SDK. Matchmaking and Lobby can be used separately or together, and real-time messages will work in either case. There's no support for real-time messages without the SDK at this time. Real-time messages aren't available as a solution for stand-alone or general use. ## How do real-time messages work Each client maintains a single WebSocket to receive real-time messages. When there are updates to Matchmaking or Lobby resources in the cloud, the SDK will forward messages in real-time to all connected clients subscribed to those resources. When a client connects to receive real-time messages, they'll open a new WebSocket connection to receive messages and listen for change events. When a client creates a lobby, joins a lobby, starts listening for invitations, or creates a Matchmaking ticket, the connected client will subscribe to a Lobby or Matchmaking resource to listen for changes. The client will be notified when there's an update on the resource topic they’ve subscribed to. For example, if a client has subscribed to a Lobby resource, they may be notified on change events like Player A or B has joined or left a Lobby. Matchmaking and Lobby documentation describe in more detail the operations that will power messages. The WebSocket connection that enables real-time messages is also used for detecting client connectivity. This client connectivity status is used by the Lobby service to power lobby ownership management. ## Shared connection support Matchmaking and Lobby messages have support to share a single WebSocket connection, which may be useful if you’re creating a title with couch co-op. Today, up to eight local users may share the WebSocket connection, and local players can be added or removed to that shared connection. Multiple users sharing the same connection can subscribe to topics to get messages for Matchmaking or Lobby events for those topics. ## Using the SDK The SDK simplifies your work for cross-network and cross-platform play by handling real-time messages for you. Messages are sent to clients on receiving invites, joining and updating lobbies, finding matches, and more. The SDK enables cross-platform play and real-time messages on any platform that PlayFab offers SDK support. Sending messages to clients is automatic, and the developer doesn't have to do any work to enable messages. ## Related topics - [Real-time messages for Lobby and Matchmaking APIs](/services/playfab/multiplayer/real-time-messages/overview.md) - [ReceiveMessage SignalR client method](/services/playfab/multiplayer/real-time-messages/client-methods/receive-message.md) - [EndSession SignalR server method](/services/playfab/multiplayer/real-time-messages/server-methods/end-session.md) - [Message real-time messages type](/services/playfab/multiplayer/real-time-messages/types/message.md) - [Subscribing to resources for real-time messages](/services/playfab/multiplayer/real-time-messages/subscribing-to-resources.md)