public void send(NetworkSend networkSend) {
    SelectionKey key = keyForId(networkSend.getConnectionId());
    if (key == null) {
      throw new IllegalStateException("Attempt to send data to a null key");
    }
    Transmission transmission = getTransmission(key);
    try {
      transmission.setNetworkSend(networkSend);
    } catch (CancelledKeyException e) {
      logger.debug("Ignoring response for closed socket.");
      close(key);
    }
  }
Queue the given request for sending in the subsequent {@link #poll(long)} calls
@param networkSend The NetworkSend that is ready to be sent
ambry-network/src/main/java/com/github/ambry/network/Selector.java