RSocket Kotlin multi-platform implementation based on kotlinx.coroutines and ktor-io.
RSocket is a binary application protocol providing Reactive Streams semantics for use on byte stream transports such as TCP, WebSockets, QUIC and Aeron.
It enables the following symmetric interaction models via async message passing over a single connection:
Learn more at http://rsocket.io
Local (in memory) transport is supported on all targets.
Most of other transports are implemented using ktor to ensure Kotlin multiplatform.
So it depends on ktor client/server engines for available transports and platforms.
| TCP | WebSocket | |
|---|---|---|
| JVM | ✅ via ktor | ✅ via ktor |
| JS | ✅ via nodeJS (not supported in browser) | ✅ via ktor |
| Native (except windows) |
✅ via ktor | ✅ via ktor |
| TCP | WebSocket | |
|---|---|---|
| JVM | ✅ via ktor | ✅ via ktor |
| JS | ✅ via nodeJS (not supported in browser) | ❌ |
| Native (except windows) |
✅ via ktor | ✅ via ktor |
rsocket-kotlin is available on Maven Central
Make sure, that you use Kotlin 1.6.20+, ktor 2.0.0+ and have mavenCentral() in the list of repositories:
repositories {
mavenCentral()
}rsocket-kotlin provides client and server plugins for ktor
Dependencies:
dependencies {
//for client
implementation("io.rsocket.kotlin:rsocket-ktor-client:0.15.4")
//for server
implementation("io.rsocket.kotlin:rsocket-ktor-server:0.15.4")
}Example of client plugin usage:
//create ktor client
val client = HttpClient {
install(WebSockets) //rsocket requires websockets plugin installed
install(RSocketSupport) {
//configure rSocket connector (all values have defaults)
connector {
maxFragmentSize = 1024
connectionConfig {
keepAlive = KeepAlive(
interval = 30.seconds,
maxLifetime = 2.minutes
)
//payload for setup frame
setupPayload {
buildPayload {
data("""{ "data": "setup" }""")
}
}
//mime types
payloadMimeType = PayloadMimeType(
data = WellKnownMimeType.ApplicationJson,
metadata = WellKnownMimeType.MessageRSocketCompositeMetadata
)
}
//optional acceptor for server requests
acceptor {
RSocketRequestHandler {
requestResponse { it } //echo request payload
}
}
}
}
}
//connect to some url
val rSocket: RSocket = client.rSocket("wss://demo.rsocket.io/rsocket")
//request stream
val stream: Flow<Payload> = rSocket.requestStream(
buildPayload {
data("""{ "data": "hello world" }""")
}
)
//take 5 values and print response
stream.take(5).collect { payload: Payload ->
println(payload.data.readText())
}Example of server plugin usage:
//create ktor server
embeddedServer(CIO) {
install(WebSockets) //rsocket requires websockets plugin installed
install(RSocketSupport) {
//configure rSocket server (all values have defaults)
server {
maxFragmentSize = 1024
//install interceptors
interceptors {
forConnection(::SomeConnectionInterceptor)
}
}
}
//configure routing
routing {
//configure route `/rsocket`
rSocket("rsocket") {
println(config.setupPayload.data.readText()) //print setup payload data
RSocketRequestHandler {
//handler for request/response
requestResponse { request: Payload ->
println(request.data.readText()) //print request payload data
delay(500) // work emulation
buildPayload {
data("""{ "data": "Server response" }""")
}
}
//handler for request/stream
requestStream { request: Payload ->
println(request.data.readText()) //print request payload data
flow {
repeat(10) { i ->
emit(
buildPayload {
data("""{ "data": "Server stream response: $i" }""")
}
)
}
}
}
}
}
}
}.start(true)rsocket-kotlin also provides standalone transports which can be used to establish RSocket connection:
Dependencies:
dependencies {
implementation("io.rsocket.kotlin:rsocket-core:0.15.4")
// TCP ktor client/server transport
implementation("io.rsocket.kotlin:rsocket-transport-ktor-tcp:0.15.4")
// WS ktor client transport
implementation("io.rsocket.kotlin:rsocket-transport-ktor-websocket-client:0.15.4")
// WS ktor server transport
implementation("io.rsocket.kotlin:rsocket-transport-ktor-websocket-server:0.15.4")
// TCP nodeJS client/server transport
implementation("io.rsocket.kotlin:rsocket-transport-nodejs-tcp:0.15.4")
}Example of usage standalone client transport:
val transport = TcpClientTransport("0.0.0.0", 8080)
val connector = RSocketConnector {
//configuration goes here
}
val rsocket: RSocket = connector.connect(transport)
//use rsocket to do request
val response = rsocket.requestResponse(buildPayload { data("""{ "data": "hello world" }""") })
println(response.data.readText())Example of usage standalone server transport:
val transport = TcpServerTransport("0.0.0.0", 8080)
val connector = RSocketServer {
//configuration goes here
}
val server: TcpServer = server.bind(transport) {
RSocketRequestHandler {
//handler for request/response
requestResponse { request: Payload ->
println(request.data.readText()) //print request payload data
delay(500) // work emulation
buildPayload {
data("""{ "data": "Server response" }""")
}
}
}
}
server.handlerJob.join() //wait for server to finish- multiplatform-chat - chat implementation with JVM/JS/Native server and JVM/JS/Native client with shared classes and shared data serialization using kotlinx.serialization
From RSocket protocol:
Reactive Streams semantics are used for flow control of Streams, Subscriptions, and Channels.
This is a credit-based model where the Requester grants the Responder credit for the number of PAYLOADs it can send.
It is sometimes referred to as "request-n" or "request(n)".
kotlinx.coroutines doesn't truly support request(n) semantic,
but it has flexible CoroutineContext which can be used to achieve something similar.
rsocket-kotlin contains RequestStrategy coroutine context element, which defines,
strategy for sending of requestNframes.
Example:
//assume we have client
val client: RSocket = TODO()
//and stream
val stream: Flow<Payload> = client.requestStream(Payload("data"))
//now we can use `flowOn` to add request strategy to context of flow
//here we use prefetch strategy which will send requestN for 10 elements, when, there is 5 elements left to collect
//so on call `collect`, requestStream frame with requestN will be sent, and then, after 5 elements will be collected
//new requestN with 5 will be sent, so collect will be smooth
stream.flowOn(PrefetchStrategy(requestSize = 10, requestOn = 5)).collect { payload: Payload ->
println(payload.data.readText())
}For bugs, questions and discussions please use the Github Issues.
Copyright 2015-2022 the original author or authors.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
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