包含stream_socket_client的单元测试类

I'm new to unit testing, but I think I understand the basics. I want to unit test a fairly simple class. (See below) I have a problem when setting up the because I don't know how to handle stream_socket_client(). I read that I should inject dependencies, but I think this would only relocate the problem with stream_socket_client() to the class injecting the client into the class ExampleProcessor as shown below.

<?php namespace App;

use Exception;

class ExampleProcessor
{
    private $client;
    private $result;

    public function __construct()
    {
        $this->client = stream_socket_client(
            "tcp://"
            . gethostbyname($_ENV['PROCESSOR_HOST'])
            . ":"
            .  $_ENV['PROCESSOR_PORT'],
            $errno,
            $errorMessage
        );

        if ($this->client === false) {
            throw new Exception();
        }
    }

    public function process($data)
    {
        $result = fwrite($this->client, $data);
        if ($result === false) {
            throw new Exception();
        }

        $this->result = stream_get_contents($this->client);
        if ($this->result === false) {
            throw new Exception();
        }

        fclose($this->client);
    }

    public function getResult()
    {
        return json_decode($this->result);
    }
}

What would be a good approach to test this class?