ch.hsr.dsl.dwrtc.websocket

Package ch.hsr.dsl.dwrtc.websocket

UI layer. Handles sending and receiving messages from the WebSocket connections.

The Message format is reused for WebSocket specific messages (WebSocketErrorMessage, WebSocketIdMessage) and application-specific messages (ClientMessage)

The WebSocketHandler consists of four main components:

WebSocketHandler.clients is a map of session ID to InternalClients
WebSocketHandler.sessions is a map of session ID to WebSocket sessions
WebSocketHandler.onReceiveMessageFromWebSocket uses the session ID to get the InternalClient. This is then used to send a message through the P2P layer
WebSocketHandler.onReceiveMessageFromSignaling uses the session ID to get the WebSocket session. This is then used to send the message to the specific WebSocket

The WebSocket session IDs, are reused for the user's session ID. The ID is assumed to be unique.

When connected to the WebSocket, an implementation can send or receive the following messages (as JSON objects).

ClientMessage. Send a black box signaling message to another peer.
- type: The message type. Has to be defined by the developer. E.g. "SignalingMessage" for WebRTC signaling messages or "CustomMessage" for custom messages.
- recipientSessionId: String. The recipient's session ID. Used for routing.
- messageBody: String. The free-form message body. To the transport layer, this is a black box. May therefore include stringified JSON.

Example:

{
	"type": "CustomMessage",
	"recipientSessionId": "ABCDEF",
	"messageBody": "Hi ABCDEF!"
}

All these incoming message types have to be handled. They are distinguishable by their type field. They are sent as JSON objects.

WebSocketIdMessage. Includes the session ID.
- type: String. Static value WebSocketIdMessage
- id: String. The session ID
WebSocketErrorMessage. Tells the implementation that something went wrong
- type: String. Static value WebSocketErrorMessage
- error: String. The error message
ClientMessage. Incoming, application-defined messages
- type: String. The message type as defined by the developer (see above)
- senderSessionId: String. The sender' session ID. Can be used to reply to messages
- recipientSessionId: String. The recipient's session ID. This should be the current session ID!
- messageBody: String. The free-form message body

WebSocketErrorMessage	`data class WebSocketErrorMessage : Message` Error messages meant for the WebSocket
WebSocketHandler	`class WebSocketHandler` Main handler class
WebSocketIdMessage	`data class WebSocketIdMessage : Message` New ID message

IDLE_TIMEOUT_MS	`const val IDLE_TIMEOUT_MS: Long` WebSocket session idle timeout in milliseconds.
WEBSOCKET_PATH	`const val WEBSOCKET_PATH: String` Path that the WebSocket handler is available on
WEB_SUB_PATH	`const val WEB_SUB_PATH: String` Sub path (to the resources directory) of the web site

main	`fun main(args: Array<String>): Unit` Main start point. Fires up the Webserver.