synchronized (PROTOCOL_HANDLERS) {
            URLStreamHandler handler = (URLStreamHandler) PROTOCOL_HANDLERS.get(protocol);
            if (handler != null) {
                return handler;
            }
            if (factory != null) {
                handler = factory.createURLStreamHandler(protocol);
            }

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;

import jcifs.smb1.util.LogStream;

/**
 * This class simplifies communication for protocols that support
 * multiplexing requests. It encapsulates a stream and some protocol
 * knowledge (provided by a concrete subclass) so that connecting,
 * disconnecting, sending, and receiving can be syncronized

        final String value = System.getProperty("java.protocol.handler.pkgs");
        if (StringUtil.isEmpty(value)) {
            buf.append("org.codelibs.fess.net.protocol");
        } else if (!value.contains("org.codelibs.fess.net.protocol")) {
            buf.append("|org.codelibs.fess.net.protocol");
        }
        if (buf.length() > 0) {
            System.setProperty("java.protocol.handler.pkgs", buf.toString());
        }
    }

    }

    /**
     * Get the protocol of the proxy server.
     *
     * @return the protocol of the proxy server
     */
    public String getProtocol() {
        return protocol;
    }

    /**
     * @param protocol the protocol of the proxy server like <i>SOCKSv4</i>
     */
    public void setProtocol(String protocol) {
        this.protocol = protocol;
    }

        val sslSocket = doSsl(socket)
        val protocolString = Platform.get().getSelectedProtocol(sslSocket)
        val protocol = if (protocolString != null) get(protocolString) else null
        if (protocol != Protocol.HTTP_2) {
          throw ProtocolException("Protocol $protocol unsupported")
        }
        val connection =
          Http2Connection
            .Builder(false, TaskRunner.INSTANCE)

  override fun secureConnectEnd(handshake: Handshake?) {
    eventListener.secureConnectEnd(call, handshake)
  }

  override fun callConnectEnd(
    route: Route,
    protocol: Protocol?,
  ) {
    eventListener.connectEnd(call, route.socketAddress, route.proxy, protocol)
  }

  override fun connectionConnectEnd(
    connection: Connection,
    route: Route,
  ) {
    poolConnectionListener.connectEnd(connection, route, call)

  }

  override fun callConnectEnd(
    route: Route,
    protocol: Protocol?,
  ) {
  }

  override fun connectionConnectEnd(
    connection: Connection,
    route: Route,
  ) {
  }

  override fun connectFailed(
    route: Route,
    protocol: Protocol?,
    e: IOException,
  ) {
  }

  override fun connectionAcquired(connection: Connection) {
  }

        // Test registerSmbURLHandler when java.protocol.handler.pkgs is null
        System.clearProperty("java.protocol.handler.pkgs");
        SingletonContext.registerSmbURLHandler();
        assertEquals("jcifs", System.getProperty("java.protocol.handler.pkgs"));
    }

    @Test
    void testRegisterSmbURLHandlerWhenPkgsDoesNotContainJcifs() {
        // Test registerSmbURLHandler when java.protocol.handler.pkgs does not contain "jcifs"

    inetSocketAddress: InetSocketAddress,
    proxy: Proxy,
    protocol: Protocol?,
  ) {
    logWithTime("connectEnd: $protocol")
  }

  override fun connectFailed(
    call: Call,
    inetSocketAddress: InetSocketAddress,
    proxy: Proxy,
    protocol: Protocol?,
    ioe: IOException,
  ) {
    logWithTime("connectFailed: $protocol $ioe")
  }

  override fun connectionAcquired(
    call: Call,

    assertThat(Protocol.SPDY_3.toString()).isEqualTo("spdy/3.1")
    assertThat(Protocol.HTTP_2.toString()).isEqualTo("h2")
    assertThat(Protocol.H2_PRIOR_KNOWLEDGE.toString())
      .isEqualTo("h2_prior_knowledge")
    assertThat(Protocol.QUIC.toString()).isEqualTo("quic")
    assertThat(Protocol.HTTP_3.toString()).isEqualTo("h3")
  }