Scarlet

A Retrofit inspired WebSocket client for Kotlin, Java, and Android.

This README is still WIP. Please see the tutorial for more information.

Tutorial

• Taming WebSocket with Scarlet
• A talk at Conference for Kotliners

Usage

In this example, we are reading the realtime Bitcoin price from Gdax WebSocket Feed. For more information, please check out the demo app.

Declare a WebSocket client using an interface.

interface GdaxService {
	@Send
	fun sendSubscribe(subscribe: Subscribe)
	@Receive
 	fun observeTicker(): Flowable<Ticker>
	@Receive
	fun observeOnConnectionOpenedEvent(): Flowable<WebSocket.Event.OnConnectionOpen<*>>
}
val gdaxService = scarlet.create<GdaxService>()

Use Scarlet to create an implementation.

val okHttpClient = OkHttpClient.Builder().build()

val scarletInstance = Scarlet.Builder()
    .webSocketFactory(okHttpClient.newWebSocketFactory("wss://ws-feed.gdax.com"))
    .addMessageAdapterFactory(MoshiMessageAdapter.Factory())
    .addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
    .build()

val gdaxService = scarletInstance.create<GdaxService>()

Send a Subscribe message upon connection open so that the server will start streaming tickers, which contain the latest price.

val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = Subscribe(
    productIds = listOf("BTC-USD"),
    channels = listOf("ticker")
)

gdaxService.observeOnConnectionOpenedEvent()
    .subscribe({
        gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
    })

Start observing realtime tickers.

gdaxService.observeTicker()
    .subscribe({ ticker ->
        Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
    })

Built-in Plugins

WebSocket.Factory

• OkHttpClient
• MockHttpServer

MessageAdapter.Factory

• moshi
• gson
• protobuf

StreamAdapter.Factory

• RxJava2
• RxJava1

Lifecycle

• AndroidLifecycle

BackoffStrategy

• Linear
• Exponential
• ExponentialWithJitter

Android

TODO:

• AndroidLifecycle

State Machine

Scarlet is driven by a StateMachine.

Download

TODO: make the jar public

Download the latest JAR or grab via Maven:

<dependency>
  <groupId>com.tinder.scarlet</groupId>
  <artifactId>scarlet</artifactId>
  <version>0.1.0</version>
</dependency>

or Gradle:

implementation 'com.tinder.scarlet:scarlet:0.1.0'

Copyright

Copyright (c) 2018, Match Group, LLC
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of Match Group, LLC nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL MATCH GROUP, LLC BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.