Web sockets make it cheaper to talk to your servers.
Connecting to a server takes some time, so with web sockets, you make that connection once and then keep using. The major benefits of this are:
It faster to send messages. No need to do a bunch of work for every single message.
The server can push messages to you. With normal HTTP you would have to keep asking for changes, but a web socket, the server can talk to you whenever it wants. This means there is less unnecessary network traffic.
Packages up your ports to put inside a State.
Opaque type, created by makeConfig.
Internal state of the WebSocketClient module.
Create one with makeState, passed to most of the other functions.
A response that your code must process to update your model.
NoResponse means there's nothing to do.
CmdResponse is a Cmd that you must return from your update function. It will send something out the sendPort in your Config.
ConnectedReponse tells you that an earlier call to send or keepAlive has successfully connected. You can usually ignore this.
MessageReceivedResponse is a message from one of the connected sockets.
ClosedResponse tells you that an earlier call to close has completed. Its code, reason, and wasClean fields are as passed by the JavaScript WebSocket interface. Its expected field will be True, if the response is to a close call on your part. It will be False if the close was unexpected, and reconnection attempts failed for 20 seconds (using exponential backoff between attempts).
ErrorResponse means that something went wrong. Details in the encapsulated Error.
All the errors that can be returned in a Response.ErrorResponse.
If an error tag has a single String arg, that string is a socket key.
This will usually be NormalClosure. The rest are standard, except for UnknownClosure, which denotes a code that is not defined, and TimeoutOutOnReconnect, which means that exponential backoff connection reestablishment attempts timed out.
The standard codes are from https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
Make a real configuration, with your input and output ports.
The parameters are:
makeConfig sendPortWhere sendPort is your output (Cmd) port.
Your input (Sub) port should wrap a Json.Encode.Value with a message,
and when your update function gets that message, it should pass it to
process, and then store the returned State in your model, and handle
the returned Response.
Make state to store in your model.
The Config arg is the result of makeConfig or makeSimulatorConfig.
Set a State's Config.
Will likely break things if you do this while connections are active.
Subscribe to any incoming messages on a websocket. You might say something like this:
type Msg = Echo String | ...
subscriptions model =
open PortVersion2 "ws://echo.websocket.org" EchoThe first arg is a PortVersion, to remind you to update your JavaScript
port code, when it changes incompatibly.
open PortVersion2 state urlKeep a connection alive, but do not report any messages. This is useful
for keeping a connection open for when you only need to send messages. So
you might say something like this:
let (state2, response) =
keepAlive state "ws://echo.websocket.org"
in
...Note: If the connection goes down, the effect manager tries to reconnect
with an exponential backoff strategy. Any messages you try to send while the
connection is down are queued and will be sent as soon as possible.
Send a message to a particular address. You might say something like this:
send PortVersion2 state "ws://echo.websocket.org" "Hello!"You must call open or openWithKey before calling send.
If you call send before the connection has been established, or while it is being reestablished after it was lost, your message will be buffered and sent after the connection has been (re)established.
The first arg is a PortVersion, to remind you to update your JavaScript
port code, if it changes incompatibly.
send PortVersion2 state key messageClose a WebSocket opened by open or keepAlive.
close state keyThe key arg is either they key arg to openWithKey or
keepAliveWithKey or the url arg to open or keepAlive.
Process a Value that comes in over the subscription port.
Like open, but allows matching a unique key to the connection.
open uses the url as the key.
openWithKey PortVersion2 state key urlLike keepAlive, but allows matching a unique key to the connection.
keeAliveWithKey state key urlMake a Config that enables running your code in elm reactor.
The arg is a server simulator, which translates a message sent with send
to a response.
Convert an Error to a string, for simple reporting.
Turn a ClosedCode into a String, for debugging.
A custom type with one tag.
The tag encodes the version of the port JavaScript code. It changes every time that code changes incompatibly, to remind you that you need to update it, and change your
open,openWithKey, andsendcalls accordingly.