server.setProtocols(Collections.singletonList(Protocol.H2_PRIOR_KNOWLEDGE));
    server.enqueue(new MockResponse().setBody("hello"));
    server.start();

    OkHttpClient client = new OkHttpClient.Builder()
        .socketFactory(new UnixDomainSocketFactory(socketFile))
        .protocols(Collections.singletonList(Protocol.H2_PRIOR_KNOWLEDGE))
        .build();

        socket.setEnabledCipherSuites(javaNames(spec.cipherSuites()));
        return socket;
      }
    };

    client = new OkHttpClient.Builder()
        .connectionSpecs(Collections.singletonList(spec))
        .sslSocketFactory(customSslSocketFactory, trustManager)
        .build();
  }

  /**
   * Returns the VM's default SSL socket factory, using {@code trustManager} for trusted root
   * certificates.

          CipherSuite.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
          CipherSuite.TLS_DHE_RSA_WITH_AES_128_GCM_SHA256)
    .build();

OkHttpClient client = new OkHttpClient.Builder()
    .connectionSpecs(Collections.singletonList(spec))
    .build();
```

### Debugging TLS Handshake Failures

The TLS handshake requires clients and servers to share a common TLS version and cipher suite. This