Web socket listener

Embedded WebSocket server: accepts WebSocket connections on a port and path, emits every received message and sends messages back to a connected client. Use it for push or chat style endpoints; reply with the listener's Input pin or a Web socket response component.

Pins

Pin	Kind	Types	Description
Start	start		Starts the server. Called by the system at flow start when unconnected.
Output	output	Viaducta.Plugins.Http.Types.WebSocketMessage	Called for every message received from any client.
Input	input	Viaducta.Plugins.Http.Types.WebSocketMessage, Viaducta.Plugins.TextPlugin.Types.TextRecord	Message to send to a client.
Authenticate	continue	Viaducta.Plugins.Http.Types.WebHttpRequest	Called before a connection is accepted. See Notes.

Configuration

Field	Type	Default	Description
ListenUrl	listener URL		Required. http://localhost:<port>/<path> (private) or http://0.0.0.0:<port>/<path> (public), e.g. http://0.0.0.0:9001/ws. Clients connect with ws://host:9001/ws.
MaxParallelRequests	integer (1-4096)	1024	Max requests processed in parallel. Further requests wait for a free slot until the caller gives up; open (keep-alive) connections are not limited.
MaxRequestBodySize	integer	0	Max request body size, 0 = unlimited.
Timeout	integer	60000	Ignored.
KeepAliveTimeout	integer	130	HTTP keep-alive timeout in seconds.
MaxRequestHeaderCount	integer	100	Max number of request headers.
UseSsl	boolean	false	true: TLS (wss://).
SslProtocol	dropdown: 0 None, 12 Ssl2, 48 Ssl3, 192 Tls, 240 Default, 768 Tls11, 3072 Tls12, 12288 Tls13	0	Allowed protocol(s) when UseSsl.
ServerCertificate	certificate		Name of a certificate object in the repository, used when UseSsl.

Behaviour

• Non-WebSocket requests get 400. If Authenticate is connected and raises an error, the handshake is answered with 401 and the error text; otherwise the connection is accepted and gets a unique session id.
• Each complete message (max 1 MB, larger messages close the connection) is emitted on Output as WebSocketMessage with SessionId, MessageType (0 text, 1 binary), ContentByte and ContentString (UTF-8). The WebSocketListener metadata carries the SessionId. Messages of one connection are processed one after another.
• Input: a TextRecord is sent as text to the session in the metadata; a WebSocketMessage is sent to its own SessionId (ContentByte wins over ContentString). An unknown session id raises an error.
• With no Output connection, clients are disconnected with a message. The plugin keeps the flow running and closes all connections when the flow stops.
• Port sharing with Http listeners follows the same rules as the Http listener (same SSL/certificate/visibility, different paths under the same first segment).

Notes

• Authenticate receives the raw ASP.NET request object, not a WebHttpRequest, and empty metadata, so Http authentification connected there does not work as with the Http listener; test any authentication branch carefully.
• If an Http listener on the same port starts first, WebSocket support is not enabled on that shared server and upgrades fail; use a separate port.
• Timeout is not used. With a single listener on a port, every path is accepted.
• To push to a client later (not as a reply), keep its SessionId and send a WebSocketMessage with that id to Input.

Example

{ "ListenUrl": "http://0.0.0.0:9001/ws" }

Web socket listener → Script (build reply) → Web socket response