val okHttpClient: OkHttpClient = ...
val httpUrl = HttpUrl.parse("string url") ?: throw IllegalArgumentException("wrong url $url")
val httpUrlBuilder = httpUrl.newBuilder()
val requestBuilder = Request.Builder().url(httpUrlBuilder.build())
requestBuilder.post(RequestBody.create(
    MediaType.parse("application/json; charset=utf-8"),
    "{"jsondata":0}")
)
val call = okHttpClient.newCall(requestBuilder.build())
call.execute()