test.kt

package okhttp3.tls

import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.tls.HandshakeCertificates.Builder

fun main() {
  val request = Request.Builder()
      .url("https://httpbin.org/get")
      .build()

  var client = OkHttpClient();
  var response = client.newCall(request).execute()

  println(response.handshake?.peerPrincipal) // CN=httpbin.org
  println(response.code)

  val certificates = Builder()
      .addInsecureHost("httpbin.org")
      .build()

  client = OkHttpClient.Builder().sslSocketFactory(certificates.sslSocketFactory(),
      certificates.trustManager
  ).build();
  response = client.newCall(request).execute()

  println(response.handshake?.peerPrincipal) // null
  println(response.code)
}