websocket

Websocket server and client in Derw

Client

The client is built around the API of constructing a connection with callbacks for onOpen / onMessage. You get back a Connection, which can be used to directly call websocket methods from the WebSocket class, however I recommend using the callbacks for the majority of processing.

type alias Socket msg = {
    url: string,
    onOpen: void -> msg,
    onMessage: string -> msg
}

type alias Connection = {
    socket: WebSocket
}

connect: Socket msg -> Connection

Server

The server is a wrapped around the ws package from Node, again built around callbacks: onConnection and onMesssage. These can be used with the Response union type to define responses to events from client connections: either wait, or send something in response.

type alias WebsocketSettings = {
    port: number,
    onConnection: Connection -> Response,
    onMessage: Connection -> string -> Response
}

type Response = Send { message: string } | Wait

It's possible to send a message to a connection without waiting, through send: Connection -> string -> void.

Running the example

See the example folder on how to use.

cd example
derw install
derw compile
derw bundle --entry src/Client.derw --output build.js

Then in two separate terminal sessions:

# open localhost://8000
python3 -m http.server

ts-node src/Server.ts