factory.init(null as KeyStore?)
    val trustManagers = factory.trustManagers!!
    check(trustManagers.size == 1 && trustManagers[0] is X509TrustManager) {
      "Unexpected default trust managers: ${trustManagers.contentToString()}"
    }
    return trustManagers[0] as X509TrustManager
  }

  open fun trustManager(sslSocketFactory: SSLSocketFactory): X509TrustManager? {
    return try {

        "Unable to find acceptable protocols." +
          " isFallback=$isTlsFallback," +
          " modes=$connectionSpecs," +
          " supported protocols=${sslSocket.enabledProtocols!!.contentToString()}",
      )
  }

  /**
   * Returns a copy of this connection with the next connection spec to try, or null if no other
   * compatible connection specs are available.
   */