// sufficient to connect to most HTTPS sites including https://godaddy.com and https://visa.com.
  // Typically developers will need to get a PEM file from their organization's TLS administrator.
  final X509Certificate comodoRsaCertificationAuthority = Certificates.decodeCertificatePem(""
      + "-----BEGIN CERTIFICATE-----\n"

 * cannot do TLS over domain sockets.
 */
public class ClientAndServer {
  public void run() throws Exception {
    File socketFile = new File("/tmp/ClientAndServer.sock");
    socketFile.delete(); // Clean up from previous runs.

    MockWebServer server = new MockWebServer();
    server.setServerSocketFactory(new UnixDomainServerSocketFactory(socketFile));
    server.setProtocols(Collections.singletonList(Protocol.H2_PRIOR_KNOWLEDGE));

    RtmStartResponse rtmStartResponse = slackApi.rtmStart(accessToken);
    webSocket = slackApi.rtm(rtmStartResponse.url, this);
  }

  // TODO(jwilson): can I read the response body? Do I have to?
  //                the body from slack is a 0-byte-buffer
  @Override public synchronized void onOpen(WebSocket webSocket, Response response) {
    System.out.println("onOpen: " + response);
  }

          .build();

      OkHttpClient clientForCall;
      if (i == 2) {
        // Force this request's response to be written to the cache. This way, subsequent responses
        // can be read from the cache.
        System.out.println("Force cache: true");
        clientForCall = client.newBuilder()
            .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)
            .build();
      } else {

import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;

/**
 * Fetches HTML from a requested URL, follows the links, and repeats.
 */
public final class Crawler {
  private final OkHttpClient client;
  private final Set<HttpUrl> fetchedUrls = Collections.synchronizedSet(new LinkedHashSet<>());

  public void run() throws Exception {
    // Use the imgur image upload API as documented at https://api.imgur.com/endpoints/image
    RequestBody requestBody = new MultipartBody.Builder()
        .setType(MultipartBody.FORM)
        .addFormDataPart("title", "Square Logo")
        .addFormDataPart("image", "logo-square.png",
            RequestBody.create(
                new File("docs/images/logo-square.png"),
                MEDIA_TYPE_PNG))