Fatal error: Uncaught Error: Class 'React\ZMQ\Context' not found

use React\EventLoop\Factory;
use React\Socket\Server as Reactor;
use React\ZMQ\Context;

{
    "require": {
        "cboden/ratchet": "^0.4.2",
        "monolog/monolog": "^2.0"
    },
    "autoload": {
        "psr-4": {
          "ColorCore\\":"core/classes/"
        }
    }
}