php将字符串写入套接字

Question

我正在尝试将字符串写入套接字。我想写的字符串是

SET 4 1

这是我写入套接字的函数

function write_to_socket($socket, $msg)
{
    $sock = socket_create(AF_UNIX, SOCK_STREAM, 0) or die("socket_create() failed: reason: ".socket_strerror(socket_last_error()));
    echo '<br>socket created<br>';

    socket_connect($sock, $socket) or die("socket_create() failed: reason: ".socket_strerror(socket_last_error()));
    echo 'Connected to '.$socket.'<br><br>';


    $length = strlen($msg);

    while (true)
    {
        echo 'Going to write '.$msg.'<br>';
        $sent = socket_write($sock, $msg, $length);
        //echo 'Read '.socket_read($sock, $length).'<br>';
        if ($sent === FALSE)
        {
            echo "could not write<br>";
            break;
        }
        // Check if the entire message has been sent
        if ($sent < $length) {
            // If not sent the entire message.
            // Get the part of the message that has not yet been sented as message
            $msg = substr($msg, $sent);
            // Get the length of the not sented part
            $length -= $sent;
            echo $length." more characters need to be writte<br>";
        }
        else
        {
            echo "Finished writing<br>";
            break;
        }
    }
    echo 'Done writing '.$msg;

    socket_close($sock);
}

此功能输出

socket created
Connected to /tmp/cool_socket

Going to write SET 4 1
Finished writing
Done writing SET 4 1

我遇到的问题是4 1被写入套接字但SET没有。我正在收听套接字并打印任何打印到它的消息。因此，一旦我将SET 4 1发送到套接字，套接字程序就输出4 1.我究竟做错了什么以及为什么SET不发送？

我调用函数的代码是这个

$i = 1;
define("RESTART", " 4");
define("SOCKET_DIRECTORY", '/tmp/');
$msg = "SET".RESTART." ".($i);
write_to_socket(SOCKET_DIRECTORY.get_socket_name($i), $msg);

其中get_socket_name（$ i）每次返回cool_socket，无论我发送什么值。

感谢任何人的帮助。