protected function getSocket($server)
    {
        if (isset($this->socket[$server])) {
            return $this->socket[$server];
        }

        $context = new ZMQContext();
        $socket = Socket::create($context, ZMQ::SOCKET_REQ, $this->logger);
        $socket->connect($server);

        $this->socket[$server] = $socket;

        return $socket;
    }