# init(session:) Creates a new group session messenger with [`GroupSessionMessenger.DeliveryMode.reliable`](/documentation/GroupActivities/GroupSessionMessenger/DeliveryMode-swift.enum/reliable) delivery mode and associates it with the specified session object. ``` init(session: GroupSession) where Activity : GroupActivity ``` ## Parameters `session` The group session to use for communication with participants. Specify a session object that is in either the [`GroupSession.State.waiting`](/documentation/GroupActivities/GroupSession/State-swift.enum/waiting) or [`GroupSession.State.joined`](/documentation/GroupActivities/GroupSession/State-swift.enum/joined) state for this parameter. However, a session must be in the joined state to send or receive messages. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)