Simple websocket server in PHP

Question

I am developing a simple websocket server in PHP. I know there are quite a few existing implementations but I want to make my own so to learn the protocol better. I managed to do the handshaking fine and my clients connect to the server. I also managed to decode the data from the client but I have problems sending back messages. The client disconnects when it receives my response. Firefox says The connection to ws://localhost:12345/ was interrupted while the page was loading..

I used this answer as a guide.

Here is my code for wrapping the data:

private function wrap($msg = ""){
    $length = strlen($msg);
    $this->log("wrapping (" . $length . " bytes): " . $msg);

    $bytesFormatted = chr(129);
    if($length <= 125){
        $bytesFormatted .= chr($length);
    } else if($length >= 126 && $length <= 65535) {
        $bytesFormatted .= chr(126);
        $bytesFormatted .= chr(( $length  >> 8 ) & 255);
        $bytesFormatted .= chr(( $length       ) & 255);
    } else {
        $bytesFormatted .= chr(127);
        $bytesFormatted .= chr(( $length >> 56 ) & 255);
        $bytesFormatted .= chr(( $length >> 48 ) & 255);
        $bytesFormatted .= chr(( $length >> 40 ) & 255);
        $bytesFormatted .= chr(( $length >> 32 ) & 255);
        $bytesFormatted .= chr(( $length >> 24 ) & 255);
        $bytesFormatted .= chr(( $length >> 16 ) & 255);
        $bytesFormatted .= chr(( $length >>  8 ) & 255);
        $bytesFormatted .= chr(( $length       ) & 255);
    }

    $bytesFormatted .= $msg;
    $this->log("wrapped (" . strlen($bytesFormatted) . " bytes): " . $bytesFormatted);
    return $bytesFormatted;
}

UPDATE: I tried it with Chrome and I got the following error, printed in the console: A server must not mask any frames that it sends to the client.

I put some console printouts on the server. It is a basic echo server. I try with aaaa. So the actual wrapped message must be 6 bytes. Right?

Chrome prints the above error. Note also that after wrapping the message I simply write it to the socket:

$sent = socket_write($client, $bytesFormatted, strlen($bytesFormatted));
$this->say("! " . $sent);

It prints 6 meaning 6 bytes are actually written to the wire.

If I try with aaa, Chrome doesn't print the error but doesn't call my onmessage handler either. It hangs as if waiting for more data.

Any help highly appreciated. Thanks.

Answer 1

I had the same problem: for some messages sent from the server there was no response in the browser, for some the error "A server must not mask any frames ..." was displayed, though I did not add any mask. The reason was in the handshake sent. The handshake was:

"HTTP/1.1 101 Web Socket Protocol Handshake\r\n" .
...
"WebSocket-Location: ws://{$host}{$resource}\r\n\r\n" . chr(0)

That chr(0) was the reason, after I removed it everything works.