Create a Vonage Video API session and generate participant tokens

Steps

1. Install the Vonage Video API server SDK for your language (e.g., @vonage/video for Node.js) and initialize it with your API key and API secret from the Vonage Dashboard.
2. Call opentok.createSession() (or the equivalent method in your SDK) with options such as mediaMode: 'routed' for server-mediated SFU routing or 'relayed' for peer-to-peer; a routed session is required for multi-party calls and server-side recording.
3. Store the returned sessionId persistently (e.g., in a database); a session represents a persistent communication context and its ID is used by all participants joining the same conversation.
4. Generate a token for each participant by calling opentok.generateToken(sessionId, { role: 'publisher', expireTime: <unix timestamp>, data: '<metadata string>' }); role can be 'subscriber', 'publisher', or 'moderator'.
5. Return the sessionId and token to your client application; the client initializes the OT (OpenTok) SDK with OT.initSession(apiKey, sessionId) and then calls session.connect(token, callback).
6. For security, generate a new token for each participant connection attempt rather than caching tokens; tokens expire after the duration set at creation (default 24 hours after generation).