dexSet = indexes.get(indexesKey);
  if (!indexSet) {
    return;
  }

  indexSet.set.delete(index);
  if (indexSet.set.size === 0) {
    indexes.delete(indexesKey);
  }
}

// Shared listen socket.
function shared(message, { handle, indexesKey, index }, cb) {
  const key = message.key;
  // Monkey-patch the close() method so we can keep track of when it's
  // closed. Avoids resource leaks when the handle is short-lived.
  const close = handle.close;

  handle.close = function() {
    send({ act: 'close', key });
    handles.delete(key);
    removeIndexesKey(indexesKey, index);
    return ReflectApply(close, handle, arguments);
  };
  assert(handles.has(key) === false);
  handles.set(key, handle);
  cb(message.errno, handle);
}

// Round-robin. Master distributes handles across workers.
function rr(message, { indexesKey, index }, cb) {
  if (message.errno)
    return cb(message.errno, null);

  let key = message.key;

  function listen(backlog) {
    // TODO(bnoordhuis) Send a message to the primary that tells it to
    // update the backlog size. The actual backlog should probably be
    // the largest requested size by any worker.
    return 0;
  }

  function close() {
    // lib/net.js treats server._handle.close() as effectively synchronous.
    // That means there is a time window between the call to close() and
    // the ack by the primary process in which we can still receive handles.
    // onconnection() below handles that by sending those handles back to
    // the primary.
    if (key === undefined)
      return;

    send({ act: 'close', key });
    handles.delete(key);
    removeIndexesKey(indexesKey, index);
    key = undefined;
  }

  function getsockname(out) {
    if (key)
      ObjectAssign(out, message.sockname);

    return 0;
  }

  // Faux handle. Mimics a TCPWrap with just enough fidelity to get away
  // with it. Fools net.Server into thinking that it's backed by a real
  // handle. Use a noop function for ref() and unref() because the control
  // channel is going to keep the worker alive anyway.
  const handle = { close, listen, ref: noop, unref: noop };

  if (message.sockname) {
    handle.getsockname = getsockname;  // TCP handles only.
  }

  assert(handles.has(key) === false);
  handles.set(key, handle);
  cb(0, handle);
}

// Round-robin connection.
function onconnection(message, handle) {
  const key = message.key;
  const server = handles.get(key);
  const accepted = server !== undefined;

  send({ ack: message.seq, accepted });

  if (accepted)
    server.onconnection(0, handle);
}

function send(message, cb) {
  return sendHelper(process, message, null, cb);
}

function _disconnect(primaryInitiated) {
  this.exitedAfterDisconnect = true;
  let waitingCount = 1;

  function checkWaitingCount() {
    waitingCount--;

    if (waitingCount === 0) {
      // If disconnect is worker initiated, wait for ack to be sure
      // exitedAfterDisconnect is properly set in the primary, otherwise, if
      // it's primary initiated there's no need to send the
      // exitedAfterDisconnect message
      if (primaryInitiated) {
        process.disconnect();
      } else {
        send({ act: 'exitedAfterDisconnect' }, () => process.disconnect());
      }
    }
  }

  handles.forEach((handle) => {
    waitingCount++;

    if (handle[owner_symbol])
      handle[owner_symbol].close(checkWaitingCount);
    else
      handle.close(checkWaitingCount);
  });

  handles.clear();
  checkWaitingCount();
}

// Extend generic Worker with methods specific to worker processes.
Worker.prototype.disconnect = function() {
  if (this.state !== 'disconnecting' && this.state !== 'destroying') {
    this.state = 'disconnecting';
    ReflectApply(_disconnect, this, []);
  }

  return this;
};

Worker.prototype.destroy = function() {
  if (this.state === 'destroying')
    return;

  this.exitedAfterDisconnect = true;
  if (!this.isConnected()) {
    process.exit(0);
  } else {
    this.state = 'destroying';
    send({ act: 'exitedAfterDisconnect' }, () => process.disconnect());
    process.once('disconnect', () => process.exit(0));
  }
};
