}
```

#### 4.5.2 Fallback TCP Provider
```java
package jcifs.internal.smb2.rdma.tcp;

public class TcpRdmaProvider implements RdmaProvider {
    @Override
    public boolean isAvailable() {
        return true;  // TCP is always available
    }
    
    @Override
    public Set<RdmaCapability> getSupportedCapabilities() {
        // TCP fallback only supports send/receive

        override fun enqueue(responseCallback: Callback) = TODO()

        override fun cancel() = TODO()

        override fun isExecuted(): Boolean = TODO()

        override fun isCanceled(): Boolean = TODO()

        override fun timeout(): Timeout = TODO()

        override fun clone(): Call = TODO()
      }
  }

  @Test
  fun callback() {
    val callback =
      object : Callback {

 * **Synchronous:** your thread blocks until the response is readable.
 * **Asynchronous:** you enqueue the request on any thread, and get [called back](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-callback/) on another thread when the response is readable.

        public RequestOptionCall<DeleteRequestBuilder> deleteOption() {
            return deleteOption;
        }
    }

    @FunctionalInterface
    public interface RequestOptionCall<OP> {
        void callback(OP op);
    }

        public RequestOptionCall<DeleteRequestBuilder> deleteOption() {
            return deleteOption;
        }
    }

    @FunctionalInterface
    public interface RequestOptionCall<OP> {
        void callback(OP op);
    }

        public RequestOptionCall<DeleteRequestBuilder> deleteOption() {
            return deleteOption;
        }
    }

    @FunctionalInterface
    public interface RequestOptionCall<OP> {
        void callback(OP op);
    }

  /** The timestamp of the last taken event, used to measure elapsed time between events. */
  private var lastTimestampNs: Long? = null

  /** Confirm that the thread does not hold a lock on `lock` during the callback. */
  fun forbidLock(lock: Any) {
    forbiddenLocks.add(lock)
  }

  /**
   * Removes recorded events up to (and including) an event is found whose class equals [eventClass]
   * and returns it.
   */

s/41584243/runtimeerror-task-attached-to-a-different-loop" class="external-link" target="_blank">MotorClient de MongoDB</a>), recuerda crear instances de objetos que necesiten un loop de eventos solo dentro de funciones async, por ejemplo, en un callback `'@app.on_event("startup")`.

///...

41584243/runtimeerror-task-attached-to-a-different-loop" class="external-link" target="_blank">MotorClient do MongoDB</a>) Lembre-se de instanciar objetos que precisam de um loop de eventos (*event loop*) apenas em funções assíncronas, e.g. um *"callback"* `'@app.on_event("startup")`.

///...

## Version 5.0.0-alpha.4

_2022-02-01_

**This release introduces fast fallback to better support mixed IPv4+IPv6 networks.** Fast fallback
is what we're calling our implementation of Happy Eyeballs, [RFC 8305][rfc_8305]. With this
feature OkHttp will attempt both IPv6 and IPv4 connections concurrently, keeping whichever connects
first. Fast fallback gives IPv6 connections a 250 ms head start so IPv6 is preferred on networks