PHP websocket |高频发送数据时出现奇怪的字符

Question

我有一个 javascript websocket 客户端和一个 php websocket 服务器。当我循环发送大量数据到服务器时，服务器窗口中出现奇怪的字符。

我发送：

setInterval(function() {
    for (var i=1; i<=5; i++) {
        WS.send("0");
    }
}, 1000);

在服务器窗口中：

Received [1]: 0╩┤&ψ╙]▬)╩Zόrcj
Received [1]: 0
Received [1]: 0≤↓ [☺ψ╧
Received [1]: 0¶╞0UoL
§╧q←%ved [1]: 0Τ
Received [1]: 0b:Ρ"6Τι
Received [1]: 0
Received [1]: 0
Received [1]: 0&Ρ┼→↑αΫ
Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0╦►╬┘Τ7■
Received [1]: 0SΖ╥m╬'έ
Received [1]: 0
Received [1]: 0,!☼┘L╡?
Received [1]: 0L│%☼ΪH§
Received [1]: 0
Received [1]: 0▀μpp┤A@
Received [1]: 0V[A√╚ύq

当我以较低的频率发送数据时，一切都很好

我发送：

setInterval(function() {
    WS.send("0");
}, 1000);

在服务器窗口中：

Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0
Received [1]: 0

为什么会这样？这正常吗？

用于取消屏蔽数据的函数：

function unmask($data) {
    $length = ord($data[1]) & 127;
    if($length == 126) {$masks = substr($data, 4, 4); $data = substr($data, 8);}
    elseif($length == 127) {$masks = substr($data, 10, 4); $data = substr($data, 14);}
    else {$masks = substr($data, 2, 4); $data = substr($data, 6);}
    $text = "";
    for ($i = 0; $i < strlen($data); ++$i) {$text .= $data[$i] ^ $masks[$i%4];}
    return $text;
}

我在这里收到消息：

while(socket_recv($client, $buffer, 2048, 0) >= 1) {
    $msg = unmask($buffer);
    echo "$msg\n";
}

Answer 1

由于Nagle's Algorithm，您的数据包中有多个 WebSocket 帧。您发送小消息的速度如此之快，以至于为了最大限度地减少网络拥塞，客户端会一直保留数据，直到它从服务器得到确认，或者直到发生合理的超时。

要解决这个问题，您只需去掉$length 的字节数，然后对剩余数据运行unmask() 函数。

您的代码也容易受到在不同数据包中拆分过大的 WebSocket 帧的影响；尝试在消息中发送超过 64KB 的数据，看看会发生什么。 （您可以再往下走，看到类似的结果；以太网的 MTU 为 1500 字节，但 TCP 本身的 MTU 为 65536 字节，因此当您发送超过 64K 时，您将始终看到碎片的影响。）

在我的服务器中，我为每个已连接的用户设置了一个缓冲区，该缓冲区被填满，直到我有一个完整的 WebSocket 帧来处理碎片，并且我只在该缓冲区的前面提取了 $header_length + $message_length 的数据时间，以防该缓冲区中有多个帧。