n onempty(self) {
      if (!self.child.connected) return;

      self.child._send({
        cmd: 'NODE_SOCKET_ALL_CLOSED',
        key: self.key
      }, undefined, true);
    }

    this.child.on('internalMessage', (msg) => {
      if (msg.key !== this.key) return;

      if (msg.cmd === 'NODE_SOCKET_NOTIFY_CLOSE') {
        // Already empty
        if (this.connections === 0) return onempty(this);

        // Wait for sockets to get closed
        this.once('empty', onempty);
      } else if (msg.cmd === 'NODE_SOCKET_GET_COUNT') {
        if (!this.child.connected) return;
        this.child._send({
          cmd: 'NODE_SOCKET_COUNT',
          key: this.key,
          count: this.connections
        });
      }
    });
  }

  add(obj) {
    this.connections++;

    // Notify the previous owner of the socket about its state change
    obj.socket.once('close', () => {
      this.connections--;

      if (this.connections === 0) this.emit('empty', this);
    });
  }
}

module.exports = { SocketListSend, SocketListReceive };