.NET - Websocket.On()

using Nitric.Sdk;
using Nitric.Sdk.Function;

var websocket = Nitric.Websocket("public");

websocket.On(WebsocketEventType.Connected, ctx => {
  // handle connections
  return ctx;
});

websocket.On(WebsocketEventType.Disconnected, ctx => {
  // handle disconnections
  return ctx;
});

websocket.On(WebsocketEventType.Message, ctx => {
  // handle message
  return ctx;
});

Nitric.Run();

Parameters

Name
eventType
Required
Required
Type
WebsocketEventType
Description
The type of websocket event to listen for. Can be Connected, Disconnected, or Message.
Name
middleware
Required
Required
Type
WebsocketMiddleware
Description
The middleware function to use as the handler for Websocket events.

Examples

Register a handler for message events

Messages can be read as literal strings using ctx.Req.Message().

websocket.On(WebsocketEventType.Message, ctx => {
    var message = ctx.Req.Message();

    Console.WriteLine($"New Message from {ctx.Req.ConnectionId}: {message}");

    return ctx;
});

Or they can be serialized to a class type using ctx.Req.Message<ClassName>().

class EventUpdate
{
    public float Status { get; set; }
    public string Content { get; set; }
}

websocket.On(WebsocketEventType.Message, ctx => {
    var message = ctx.Req.Message<EventUpdate>();

    Console.WriteLine($"Status: {message.Status}, Message: {message.Content}")

    return ctx;
});

Manage Websocket connections

To store Websocket connections you can use a Nitric collection.

using System;
using Nitric.Sdk.Function;
using Nitric.Sdk.Resource;

class OpenConnection
{
    public string Id { get; set; }
    public Dictionary<string, string> Metadata { get; set; }
}

var websocket = Nitric.Websocket("public");

var collections = Nitric.Collection<OpenConnection>("connections").With(
    CollectionPermission.Writing, CollectionPermission.Deleting
);

websocket.On(WebsocketEventType.Connected, ctx =>
{
    collections.Doc(ctx.Req.ConnectionId).Set(new OpenConnection
    {
        Id = ctx.Req.ConnectionId,
        Metadata = new Dictionary<string, string> { } // store any metadata related to the connection here
    });
    return ctx;
});

websocket.On(WebsocketEventType.Disconnected, ctx =>
{
    collections.Doc(ctx.Req.ConnectionId).Delete();
    return ctx;
});

Nitric.Run();

Chain functions as a single method handler

using System;
using Nitric.Sdk.Function;

class Application
{
    static WebsocketContext ValidateRequest(WebsocketContext ctx, Func<WebsocketContext, WebsocketContext> next)
    {
        // Validate Request
        return next(ctx);
    }

    static WebsocketContext HandleRequest(WebsocketContext ctx, Func<WebsocketContext, WebsocketContext> next)
    {
        // Handle Request
        return next(ctx);
    }

    public static void Main(string[] args) {
        var websocket = Nitric.Websocket("public");

        websocket.On(WebsocketNotificationType.Message, ValidateRequest, HandleRequest);

        Nitric.Run();
    }
}