HTTP_1_0.protocol -> HTTP_1_0
        HTTP_1_1.protocol -> HTTP_1_1
        H2_PRIOR_KNOWLEDGE.protocol -> H2_PRIOR_KNOWLEDGE
        HTTP_2.protocol -> HTTP_2
        SPDY_3.protocol -> SPDY_3
        QUIC.protocol -> QUIC
        else -> {
          // Support HTTP3 draft like h3-29
          if (protocol.startsWith(HTTP_3.protocol)) HTTP_3 else throw IOException("Unexpected protocol: $protocol")
        }

        // Pick the first known protocol the peer advertises.
        for (i in 0..peerProtocols.size) {
          val protocol = peerProtocols[i] as String
          if (protocol in protocols) {
            selected = protocol
            return selected
          }
        }
        selected = protocols[0] // On no intersection, try peer's first protocol.
        return selected

     * 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)
      }
      return result.readByteArray()
    }

      .host(uriHost)
      .port(uriPort)
      .build()

  /**
   * The protocols the client supports. This method always returns a non-null list that
   * contains minimally [Protocol.HTTP_1_1].
   */
  @get:JvmName("protocols")
  val protocols: List<Protocol> = protocols.toImmutableList()

  @get:JvmName("connectionSpecs")
  val connectionSpecs: List<ConnectionSpec> =

          .build()
      }
    assertThat(e).hasMessage("expected a null request body with 'Connection: upgrade'")
  }

  private fun enableTls(vararg protocols: Protocol) {
    client =
      client
        .newBuilder()
        .protocols(protocols.toList())
        .sslSocketFactory(
          handshakeCertificates.sslSocketFactory(),
          handshakeCertificates.trustManager,

  override fun configureTlsExtensions(
    sslSocket: SSLSocket,
    hostname: String?,
    protocols: List<Protocol>,
  ) {
    getDelegate(sslSocket)?.configureTlsExtensions(sslSocket, hostname, protocols)
  }

  override fun getSelectedProtocol(sslSocket: SSLSocket): String? = getDelegate(sslSocket)?.getSelectedProtocol(sslSocket)

    try {
      // SSLSocket.getApplicationProtocol returns "" if application protocols values will not
      // be used. Observed if you didn't specify SSLParameters.setApplicationProtocols
      when (val protocol = sslSocket.applicationProtocol) {
        null, "" -> null
        else -> protocol
      }
    } catch (e: UnsupportedOperationException) {

      super.configureTlsExtensions(sslSocket, hostname, protocols)
    }
  }

  override fun getSelectedProtocol(sslSocket: SSLSocket): String? =
    if (sslSocket is BCSSLSocket) {
      when (val protocol = (sslSocket as BCSSLSocket).applicationProtocol) {
        // Handles both un-configured and none selected.
        null, "" -> null
        else -> protocol
      }
    } else {
      super.getSelectedProtocol(sslSocket)
    }

    } else {
      super.configureTlsExtensions(sslSocket, hostname, protocols)
    }
  }

  override fun getSelectedProtocol(sslSocket: SSLSocket): String? =
    if (sslSocket is org.openjsse.javax.net.ssl.SSLSocket) {
      when (val protocol = sslSocket.applicationProtocol) {
        // Handles both un-configured and none selected.
        null, "" -> null
        else -> protocol
      }
    } else {

    val s = sslSocket as BCSSLSocket

    return when (val protocol = s.applicationProtocol) {
      null, "" -> null
      else -> protocol
    }
  }

  override fun configureTlsExtensions(
    sslSocket: SSLSocket,
    hostname: String?,
    protocols: List<Protocol>,
  ) {
    // No TLS extensions if the socket class is custom.
    if (matchesSocket(sslSocket)) {