setHostname.invoke(sslSocket, hostname)
        }

        // Enable ALPN.
        setAlpnProtocols.invoke(
          sslSocket,
          Platform.concatLengthPrefixed(protocols),
        )
      } catch (e: IllegalAccessException) {
        throw AssertionError(e)
      } catch (e: InvocationTargetException) {
        throw AssertionError(e)
      }
    }
  }

    /**
     * Returns the concatenation of 8-bit, length prefixed protocol names.
     * http://tools.ietf.org/html/draft-agl-tls-nextprotoneg-04#page-4
     */
    fun concatLengthPrefixed(protocols: List<Protocol>): ByteArray {
      val result = Buffer()
      for (protocol in alpnProtocolNames(protocols)) {
        result.writeByte(protocol.length)
        result.writeUtf8(protocol)
      }