i keep getting No such file or directory error and cant figure out why

<?php
$servername= 'localhost';
$username= 'root';
$pass= '';
$database_name= 'login';

$conn = mysqli_connect($server_name, $username, $pass, $database_name);

if(!$conn)
{
    die("Connection Failed: " . mysqli_connect_error());
}

if(isset($_POST['save']))
{
    $user_name = $_POST['user_name'];
    $password = $_POST['password'];

    $sql_query = "INSERT INTO entry_details (user_name,password) VALUES('$user_name','password')";

    if (mysqli_query($conn, $sql_query))
    {
        echo "Registered Successfully!!";
    }
    else
    {
        echo "Error: ". $sql ."". mysqli_error($conn);
    }
    mysqli_close($conn);
}

results-> Warning: mysqli_connect(): (HY000/2002): No such file or directory in /home/public/conn.php on line 7 Connection Failed: No such file or directory

conn.php is in that directory though. I feel its a simple fix