HcHttpClient (abstract base class)
    ├── Hc4HttpClient
    └── Hc5HttpClient
```

Switch via system property: `-Dfess.crawler.http.client=hc4` or `hc5` (default)

**Key Properties**: `connectionTimeout`, `soTimeout`, `proxyHost`, `proxyPort`, `userAgent`, `robotsTxtEnabled`, `ignoreSslCertificate`, `maxTotalConnection`, `defaultMaxConnectionPerRoute`

### CrawlerClientFactory

Pattern-based client selection (from `crawler/client.xml`):

        Map<String, String> validParams = new HashMap<>();
        validParams.put("jcifs.smb.client.domain", "TEST_DOMAIN");
        validParams.put("jcifs.smb.client.soTimeout", "300000");

        when(servletConfig.getInitParameterNames()).thenReturn(Collections.enumeration(validParams.keySet()));

     *
     * @return send buffer size, in bytes
     */
    int getSendBufferSize();

    /**
     *
     * Property {@code jcifs.smb.client.soTimeout} (int, default 35000)
     *
     * @return socket timeout, in milliseconds
     */
    int getSoTimeout();

    /**
     *
     * Property {@code jcifs.smb.client.connTimeout} (int, default 35000)

    private static final int RCV_BUF_SIZE = Config.getInt("jcifs.smb1.netbios.rcv_buf_size", DEFAULT_RCV_BUF_SIZE);
    private static final int SO_TIMEOUT = Config.getInt("jcifs.smb1.netbios.soTimeout", DEFAULT_SO_TIMEOUT);
    private static final int RETRY_COUNT = Config.getInt("jcifs.smb1.netbios.retryCount", DEFAULT_RETRY_COUNT);

    this.rawSocket = rawSocket

    // Handle the race where cancel() precedes connectSocket(). We don't want to miss a cancel.
    if (canceled) {
      throw IOException("canceled")
    }

    rawSocket.soTimeout = socketReadTimeoutMillis
    try {
      Platform.get().connectSocket(rawSocket, route.socketAddress, socketConnectTimeoutMillis)
    } catch (e: ConnectException) {

                logger.debug("Skipping availability check. llmType={}, name={}", getLlmType(), getName());
            }
            return;
        }

        final int timeout = getTimeout();
        final RequestConfig requestConfig = RequestConfig.custom()
                .setConnectionRequestTimeout(Timeout.ofMilliseconds(timeout))
                .setResponseTimeout(Timeout.ofMilliseconds(timeout))

-XX:MaxGCPauseMillis=60000\n\
-XX:G1NewSizePercent=5\n\
-XX:G1MaxNewSizePercent=5\n\
-Djcifs.smb.client.responseTimeout=30000\n\
-Djcifs.smb.client.soTimeout=35000\n\
-Djcifs.smb.client.connTimeout=60000\n\
-Djcifs.smb.client.sessionTimeout=60000\n\
-Djcifs.smb1.smb.client.connTimeout=60000\n\
-Djcifs.smb1.smb.client.soTimeout=35000\n\
-Djcifs.smb1.smb.client.responseTimeout=30000\n\
-Dio.netty.noUnsafe=true\n\
-Dio.netty.noKeySetOptimization=true\n\

        final byte[] buf = new byte[1024];
        int n;
        String name;

        final Properties p = new Properties();
        p.putAll(System.getProperties());
        p.setProperty("jcifs.smb.client.soTimeout", "600000");
        p.setProperty("jcifs.smb.client.attrExpirationPeriod", "300000");

        final Enumeration<String> e = getInitParameterNames();
        while (e.hasMoreElements()) {

        InputStream is;
        final StringBuilder sb = new StringBuilder();
        final byte[] buf = new byte[1024];
        int n, level;
        String name;

        Config.setProperty("jcifs.smb1.smb.client.soTimeout", "600000");
        Config.setProperty("jcifs.smb1.smb.client.attrExpirationPeriod", "300000");

        final Enumeration e = getInitParameterNames();
        while (e.hasMoreElements()) {

     * -XX:G1MaxNewSizePercent=5<br>
     * -Djcifs.smb.client.responseTimeout=30000<br>
     * -Djcifs.smb.client.soTimeout=35000<br>
     * -Djcifs.smb.client.connTimeout=60000<br>
     * -Djcifs.smb.client.sessionTimeout=60000<br>
     * -Djcifs.smb1.smb.client.connTimeout=60000<br>
     * -Djcifs.smb1.smb.client.soTimeout=35000<br>
     * -Djcifs.smb1.smb.client.responseTimeout=30000<br>
     * -Dio.netty.noUnsafe=true<br>