*  **There is no longer a global singleton connection pool.** In OkHttp 2.x,
    all `OkHttpClient` instances shared a common connection pool by default.
    In OkHttp 3.x, each new `OkHttpClient` gets its own private connection pool.
    Applications should avoid creating many connection pools as doing so
    prevents connection reuse. Each connection pool holds its own set of

// ValidateAuthFn should check authentication for the given aud.
type ValidateAuthFn func(auth string) string

// Connection will return the connection for the specified host.
// If the host does not exist nil will be returned.
func (m *Manager) Connection(host string) *Connection {
	return m.targets[host]
}

// RegisterSingleHandler will register a stateless handler that serves

     *
     * * **Stale pooled connections.** The [ConnectionPool] reuses sockets
     *   to decrease request latency, but these connections will occasionally time out.
     *
     * * **Unreachable proxy servers.** A [ProxySelector] can be used to
     *   attempt multiple proxy servers in sequence, eventually falling back to a direct
     *   connection.
     *

A **Manager** is used to manage all incoming and outgoing connections to a server.

On startup all remote servers must be specified.
From that individual connections will be spawned to each remote server,
or incoming requests will be hooked up to the appropriate connection.

To get a connection to a specific server, use `Manager.Connection(host)` to get a connection to the specified host.
From this connection individual requests can be made.

_2020-03-08_

 *  Fix: Don't reuse a connection on redirect if certs match but DNS does not. For better
    locality and performance OkHttp attempts to use the same pooled connection across redirects and
    follow-ups. It independently shares connections when the IP addresses and certificates match,
    even if the host names do not. In 4.4.0 we introduced a regression where we shared a connection

 * Fix: Respect read timeouts on recycled connections.
 * Fix: Transmit multiple cookie values as a single header with delimiter.
 * Fix: Ensure `null` is never returned from a connection's `getHeaderFields()`.
 * Fix: Persist proper `Content-Encoding` header to cache for GZip responses.
 * Fix: Eliminate rare race condition in SPDY streams that would prevent connection reuse.

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test
  public void equivalent_directedVsUndirected() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(oppositeType(edgeType));
    g2.addEdge(N1, N2, E12);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets and node/edge connections are the same, but directedness differs.
  @Test

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test
  public void equivalent_directedVsUndirected() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(oppositeType(edgeType));
    g2.addEdge(N1, N2, E12);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets and node/edge connections are the same, but directedness differs.
  @Test

import okhttp3.internal.isHealthy
import okhttp3.internal.tls.OkHostnameVerifier
import okio.Buffer

/**
 * A connection to a remote web server capable of carrying 1 or more concurrent streams.
 *
 * Connections are shared in a connection pool. Accesses to the connection's state must be guarded
 * by holding a lock on the connection.
 */
class RealConnection internal constructor(
  val taskRunner: TaskRunner,

    /** Array of Windows error messages corresponding to WINERR_CODES */
    String[] WINERR_MESSAGES = { "The operation completed successfully.", "Access is denied.",
            "No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept.",
            "The pipe state is invalid.", "All pipe instances are busy.", "The pipe is being closed.",