kotlin example of OKHttp3 WSS

MainActivity.kt

/**
don't forget to add in app gradle:
    compile 'com.squareup.retrofit2:retrofit:2.3.0'

and add INTERNET permission to AndroidManifest
  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
   ...>
    <uses-permission android:name="android.permission.INTERNET" />
    <application... /> 
    />
**/
import android.os.Bundle
import android.support.design.widget.BottomNavigationView
import android.support.v7.app.AppCompatActivity
import android.util.Log
import kotlinx.android.synthetic.main.activity_main.*
import okhttp3.*
import ru.biatech.apptemplate.R
import java.util.concurrent.TimeUnit
import okio.ByteString

class MainActivity : AppCompatActivity() {

    private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
        when (item.itemId) {
            R.id.navigation_home -> {
                message.setText(R.string.title_home)
                return@OnNavigationItemSelectedListener true
            }
            R.id.navigation_dashboard -> {
                message.setText(R.string.title_dashboard)
                return@OnNavigationItemSelectedListener true
            }
            R.id.navigation_notifications -> {
                message.setText(R.string.title_notifications)
                return@OnNavigationItemSelectedListener true
            }
        }
        false
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)

        // wss test
        val client = OkHttpClient.Builder()
                .readTimeout(3, TimeUnit.SECONDS)
                //.sslSocketFactory() - ? нужно ли его указывать дополнительно
                .build()
        val request = Request.Builder()
                .url("wss://echo.websocket.org") // 'wss' - для защищенного канала
                .build()
        val wsListener = EchoWebSocketListener ()
        val webSocket = client.newWebSocket(request, wsListener) // this provide to make 'Open ws connection'
    }
}

private class EchoWebSocketListener : WebSocketListener() {
    override fun onOpen(webSocket: WebSocket, response: Response) {
        webSocket.send("Hello, it's SSaurel !")
        webSocket.send("What's up ?")
        webSocket.send(ByteString.decodeHex("deadbeef"))
        webSocket.close(NORMAL_CLOSURE_STATUS, "Goodbye !")
    }

    override fun onMessage(webSocket: WebSocket?, text: String?) {
        output("Receiving : " + text!!)
    }

    override fun onMessage(webSocket: WebSocket?, bytes: ByteString?) {
        output("Receiving bytes : " + bytes!!.hex())
    }

    override fun onClosing(webSocket: WebSocket?, code: Int, reason: String?) {
        webSocket!!.close(NORMAL_CLOSURE_STATUS, null)
        output("Closing : $code / $reason")
    }

    override fun onFailure(webSocket: WebSocket, t: Throwable, response: Response) {
        output("Error : " + t.message)
    }

    companion object {
        private val NORMAL_CLOSURE_STATUS = 1000
    }

    private fun output(txt: String) {
        Log.v("WSS", txt)
    }
}

Alternative way - using of NV library

• add to gradle:
  compile 'com.neovisionaries:nv-websocket-client:2.3'

And change code to next:
`override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)

    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)

    // just stupid rx to call WSS NOT(!) on MainThread
    Observable.just("Hello World")
            .subscribeOn(Schedulers.newThread())
            .observeOn(Schedulers.newThread())
            .subscribe({
                smth ->
                    testWSS() // !!! must be not on the MainThread
            })
}

private fun testWSS() {
    // Create a WebSocket with a socket connection timeout value.
    val ws = WebSocketFactory().createSocket("wss://echo.websocket.org", 5000)

    // Register a listener to receive WebSocket events.
    ws.addListener(object : WebSocketAdapter() {
        override fun onTextMessage(websocket: WebSocket?, text: String?) {
            super.onTextMessage(websocket, text)
            Log.v("WSS", text)
        }

        override fun onCloseFrame(websocket: WebSocket?, frame: WebSocketFrame?) {
            super.onCloseFrame(websocket, frame)
            Log.v("WSS", "closing socket")
        }
    })

    ws.connect()
    ws.sendText("hello !")
    ws.disconnect()
}`