Android/Kotlin: OkHttp3를 사용하여 WebSocket 통신을 하는 법

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1. AndroidManifest.xml에 작성

<uses-permission android:name="android.permission.INTERNET" />

2. build.gradle(Module)에 작성

dependencies {
    implementation 'com.squareup.okhttp3:okhttp:3.12.12'
    ...
}

3. ListenerClass 생성

import android.util.Log
import okhttp3.Response
import okhttp3.WebSocket
import okhttp3.WebSocketListener
import okio.ByteString

class WebSocketListener : WebSocketListener() {
    override fun onOpen(webSocket: WebSocket, response: Response?) {
        webSocket.send("{\"type\":\"ticker\", \"symbols\": [\"BTC_KRW\"], \"tickTypes\": [\"30M\"]}")
        webSocket.close(NORMAL_CLOSURE_STATUS, null) //없을 경우 끊임없이 서버와 통신함
    }

    override fun onMessage(webSocket: WebSocket?, text: String) {
        Log.d("Socket","Receiving : $text")
    }

    override fun onMessage(webSocket: WebSocket?, bytes: ByteString) {
        Log.d("Socket", "Receiving bytes : $bytes")
    }

    override fun onClosing(webSocket: WebSocket, code: Int, reason: String) {
        Log.d("Socket","Closing : $code / $reason")
        webSocket.close(NORMAL_CLOSURE_STATUS, null)
        webSocket.cancel()
    }

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

    companion object {
        private const val NORMAL_CLOSURE_STATUS = 1000
    }
}

webSocket.send()를 통해 서버로 메시지를 보낸다.

override fun onMessage()를 통해 서버로부터 메시지를 받는다.

4. 사용방법

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import okhttp3.OkHttpClient
import okhttp3.Request

class MainActivity : AppCompatActivity() {

    private lateinit var client: OkHttpClient

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

        client = OkHttpClient()

        val request: Request = Request.Builder()
            .url("wss://pubwss.bithumb.com/pub/ws")
            .build()
        val listener: WebSocketListener = WebSocketListener()

        client.newWebSocket(request, listener)
        client.dispatcher().executorService().shutdown()
    }
}