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?

enter image description here

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.

Have you used wireshark to check that the bytes being sent over the wire match what appears to be generated in the code here? And that no other bit of code is sending additional data which might be interpreted as the start of a message? — simonc
– simonc, Commented Oct 29, 2012 at 15:56
@simonc It is on the same machine so I think wireshark can't see the packages. I will try to sniff it somehow. Thanks. — Martin Dimitrov
– Martin Dimitrov, Commented Oct 29, 2012 at 16:38
Do you have a second machine you could temporarily run Firefox on? — simonc
– simonc, Commented Oct 29, 2012 at 16:45
@DaveKok chr(129) returns one byte. pack('c', 129) also returns one byte. See codepad.org/N3KWIXTq — Martin Dimitrov
– Martin Dimitrov, Commented Nov 1, 2012 at 18:21

Alan Smith · Accepted Answer · 2012-11-08 18:55:31Z

4

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.

answered Nov 8, 2012 at 18:55

Alan Smith

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jbrinkley · Accepted Answer · 2012-11-08 00:00:10Z

0

When I wrote my websocket classes, I had the same issue. In my case, I used output buffering to determine that I was echo'ing something out before I sent the reply. Might try that and see if it's the problem.

answered Nov 8, 2012 at 0:00

jbrinkley

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