@Throws(IOException::class)
  fun connectionPreface() {
    withLock {
      if (closed) throw IOException("closed")
      if (!client) return // Nothing to write; servers don't send connection headers!
      if (logger.isLoggable(FINE)) {
        logger.fine(format(">> CONNECTION ${CONNECTION_PREFACE.hex()}"))
      }
      sink.write(CONNECTION_PREFACE)
      sink.flush()
    }
  }

    /**
     * Get the value for the key 'mail.send.mock'. <br>
     * The value is, e.g. true <br>
     * comment: Does it send mock mail? (true: no send actually, logging only)
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getMailSendMock();

    /**
     * Is the property for the key 'mail.send.mock' true? <br>
     * The value is, e.g. true <br>

  ) : SocketEffect

  /**
   * On HTTP/2, send a [GOAWAY frame](https://tools.ietf.org/html/rfc7540#section-6.8) immediately
   * after the response and will close the connection when the client's socket is exhausted.
   *
   * On HTTP/1 this closes the socket.
   */
  public object ShutdownConnection : SocketEffect

  /**
   * On HTTP/2 this will send the error code on the stream.
   *

  override fun send(text: String): Boolean = send(text.encodeUtf8(), OPCODE_TEXT)

  override fun send(bytes: ByteString): Boolean = send(bytes, OPCODE_BINARY)

  @Synchronized private fun send(
    data: ByteString,
    formatOpcode: Int,
  ): Boolean {
    // Don't send new frames after we've failed or enqueued a close frame.

							bucket, version.Name, err))
					}
				}

				if !send(result) {
					return
				}
			}

			// All versions resulted in 'ObjectNotFound/VersionNotFound'
			if versionNotFound == len(fivs.Versions) {
				return
			}

			send(healEntryDone(entry.name))

			// Wait and proceed if there are active requests
			waitForLowHTTPReq()
		}

        // For now, we're preparing the request structure correctly

        // TODO: Integration point - send request through session.send()
        // Smb2IoctlResponse response = (Smb2IoctlResponse) session.send(request);
        // if (response.isSuccess()) {
        //     parseNetworkInterfaces(response.getOutputData());
        // }

            message.setFlags(request.getFlags());
            message.setTimeout((int) (context.getConfig().getWitnessRegistrationTimeout() / 1000));

            // Send the RPC request
            rpcHandle.sendrecv(message);

            // Create response from RPC message results
            WitnessRegisterResponse response = new WitnessRegisterResponse();

	retryTicker := time.NewTicker(retryInterval)
	defer retryTicker.Stop()

	send := func(key Key) bool {
		for {
			err := target.SendFromStore(key)
			if err == nil {
				break
			}

			logger(
				context.Background(),
				fmt.Errorf("unable to send log entry to '%s' err '%w'", target.Name(), err),
				target.Name(),
			)

			select {

```mermaid
sequenceDiagram
    participant App
    participant Client

    App->>App: Produce Item 1
    App->>Client: Send Item 1
    App->>App: Produce Item 2
    Client->>Client: Process Item 1
    App->>Client: Send Item 2
    App->>App: Produce Item 3
    Client->>Client: Process Item 2
    App->>Client: Send Item 3
    Client->>Client: Process Item 3
    Note over App: Keeps producing...
    Note over Client: Keeps consuming...

import org.codelibs.fess.mylasta.mail.EsStatusPostcard;
import org.codelibs.fess.opensearch.client.SearchEngineClient;
import org.codelibs.fess.util.ComponentUtil;
import org.dbflute.mail.send.hook.SMailCallbackContext;
import org.lastaflute.core.mail.Postbox;

/**
 * Job for pinging search engine.
 */
public class PingSearchEngineJob {

    /**
     * Default constructor.
     */