* When making TLS connections with multiple [connection specs](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection-spec/), these are attempted in sequence until the TLS handshake succeeds.

### [Connections](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection/)

Specific security vs. connectivity decisions are implemented by [ConnectionSpec](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection-spec/). OkHttp includes four built-in connection specs:

 * `RESTRICTED_TLS` is a secure configuration, intended to meet stricter compliance requirements.
 * `MODERN_TLS` is a secure configuration that connects to modern HTTPS servers.

    }
  } finally {
    client.dispatcher.executorService.shutdownNow()
    client.connectionPool.evictAll()
  }
}

private fun buildClient(vararg specs: ConnectionSpec): OkHttpClient {
  return OkHttpClient.Builder()
    .connectionSpecs(listOf(*specs))
    .build()
}

private fun sendRequest(
  client: OkHttpClient,
  url: String,
) {
  System.out.printf("%-40s ", url)
  System.out.flush()

    internal var sslSocketFactoryOrNull: SSLSocketFactory? = null
    internal var x509TrustManagerOrNull: X509TrustManager? = null
    internal var connectionSpecs: List<ConnectionSpec> = DEFAULT_CONNECTION_SPECS
    internal var protocols: List<Protocol> = DEFAULT_PROTOCOLS
    internal var hostnameVerifier: HostnameVerifier = OkHostnameVerifier
    internal var certificatePinner: CertificatePinner = CertificatePinner.DEFAULT

import assertk.assertions.isEqualTo
import assertk.assertions.isNull
import assertk.assertions.matches
import java.math.BigInteger
import java.security.KeyFactory
import java.security.spec.PKCS8EncodedKeySpec
import java.security.spec.X509EncodedKeySpec
import java.util.concurrent.TimeUnit
import okhttp3.testing.PlatformRule
import okhttp3.tls.HeldCertificate.Companion.decode
import okio.ByteString.Companion.decodeBase64

    // we rule out characters that would cause problems in host headers.
    if (c <= '\u001f' || c >= '\u007f') {
      return true
    }
    // Check for the characters mentioned in the WHATWG Host parsing spec:
    // U+0000, U+0009, U+000A, U+000D, U+0020, "#", "%", "/", ":", "?", "@", "[", "\", and "]"
    // (excluding the characters covered above).
    if (" #%/:?@[\\]".indexOf(c) != -1) {
      return true
    }
  }

    memory if web socket compression is negotiated but not used.


## Version 4.5.0-RC1

_2020-03-17_

**This release candidate turns on web socket compression.**

The [spec][rfc_7692] includes a sophisticated mechanism for client and server to negotiate
compression features. We strive to offer great performance in our default configuration and so we're

   */
  fun merge(other: Settings) {
    for (i in 0 until COUNT) {
      if (!other.isSet(i)) continue
      set(i, other[i])
    }
  }

  companion object {
    /**
     * From the HTTP/2 specs, the default initial window size for all streams is 64 KiB. (Chrome 25
     * uses 10 MiB).
     */
    const val DEFAULT_INITIAL_WINDOW_SIZE = 65535

        return buildRedirectRequest(userResponse, method)
      }

      HTTP_CLIENT_TIMEOUT -> {
        // 408's are rare in practice, but some servers like HAProxy use this response code. The
        // spec says that we may repeat the request without modifications. Modern browsers also
        // repeat the request (even non-idempotent ones.)
        if (!client.retryOnConnectionFailure) {

    for each. This changes `Address` to no longer use `ConnectionSpec`. (This is
    an incompatible API change).

 *  **`FormEncodingBuilder` now uses `%20` instead of `+` for encoded spaces.**
    Both are permitted-by-spec, but `%20` requires fewer special cases.

 *  **Okio has been updated to 1.4.0.**
     ```xml
     <dependency>
       <groupId>com.squareup.okio</groupId>
       <artifactId>okio</artifactId>