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POGWAN Bidirectional Communication using websockets
 

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  1. POGWAN Bidirectional Communication using websockets
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    <p><strong>Solved</strong></p> <p>My solution for the read problem was to move the code to a handler, and there using HDL_AFTER_READ state to handle the websocket connection. After putting handshake to reply buffer, return 2 to send it. Additionally you might want to change KALIVE_TMO, as that dictates after how much time the connection is closed if there is no traffic. I've still not gotten the whole websocket thing finished, as I can't seem to identify the connection afterwards (US_REQUEST_DATA doesn't work here), but that's a different topic and I only mention it here so people know why I'm not (yet) updating my code.</p> <p>-- Original question:</p> <p>I'm currently in the process of trying to get websockets to work with GWAN (<a href="http://gwan.com" rel="nofollow">http://gwan.com/</a>) 4.3.14. So far I've gotten past the connection handshake with firefox/chrome, but afterwards the connection closes after a few seconds. </p> <p>I already have a guess why this is happening, which is probably the missing PONG from the server, but my problem now is, I can't figure out how to read more data from the client from a servlet. I've found that it seems to be possible to do that from a handler (at least according to the manual, which I've found to be wrong/outdated a couple of times), but there also seem to be a couple of possibilities using servlets which I'd prefer.</p> <p>So far I've tried: - wake_up with WK_FD on file_fd of get_env(argv, HTTP_HEADERS) ; wake_up doesn't seem to work no matter what I do (tried using WK_MS with values between 1000 and 100000 with no difference - servlet was called again instantly after returning RC_NOHEADERS + RC_STREAMING) - recv on get_env(argv, CLIENT_SOCKET) ; here recv tells me that whatever I'm operating on (int with value 0) is not a socket (never got CLIENT_SOCKET to work in the past either, I must be doing something wrong there?) - simple sleep(1) (up to 20) calls - READ_XBUF does not have new data afterwards, even if wireshark on the client + tcpdump on the server tells me that there is data going from client to server</p> <p>I've also tried using different handler states returning 1 for "read more data from client" in the past (some versions ago, so maybe this is already fixed - but as said, I'd prefer a solution with servlets). This didn't even work with a simple ajax post request (most browsers send post data in a second tcp packet when using post, so you don't initially get the payload with gwan), so no luck there either.</p> <p>P.S: On a sidenote (as I know Gil is answering most if not all gwan related questions here), I've wanted to sign up for a hobbyist support contract on GWAN website a few times already, but I've not found out how to get past the initial price list (which isn't available in euro as of the time of writing this).</p> <p>I'll gladly provide any kind of code which could help solving this,</p> <p>Thank you very much for your time.</p> <p>Edit: Code of main function (I know that the termination code is wrong, so please ignore it for now, as that is also not the reason for my question here)</p> <pre><code>printf("\n---------- RUN ---------\n"); xbuf_t *reply = get_reply(argv); xbuf_t *request = (xbuf_t *)get_env(argv, READ_XBUF); void **pdata = (void**)get_env(argv, US_REQUEST_DATA); if (!pdata[0]) { // no request data yet, send upgrade to websocket char *upgrade = xbuf_findstr(request, "\r\nUpgrade: websocket\r\n"); // FF only sends this ; chrome also sends "Connection: Upgrade\r\n" afterwards if (upgrade != NULL) { // correct upgrade header found? const char keyHeader[] ="\r\nSec-WebSocket-Key: "; char *key = xbuf_findstr(request, (char *)keyHeader); if (key != NULL &amp;&amp; (key += sizeof(keyHeader) - 1) != NULL &amp;&amp; (request-&gt;len - (u32)(key - request-&gt;ptr)) &gt;= (u32)23) { // correct key header found? + sanity check char websocketGUID[] = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"; // 8 + 4 + 4 + 4 + 12 = 32 + 4 bytes for '-' = 36 const char data[] = "HTTP/1.1 101 Switching Protocols\r\nUpgrade: websocket\r\nConnection: Upgrade\r\nSec-WebSocket-Accept: %20B\r\n\r\n"; // 36 + 24 char keyCompose[60]; strncpy(keyCompose, key, 24); strncpy(keyCompose + 24, websocketGUID, 36); u8 sha[20]; sha1_t ctx; sha1_init(&amp;ctx); sha1_add(&amp;ctx, (u8 *)keyCompose, 60); sha1_end(&amp;ctx, sha); xbuf_xcat(reply, (char *)data, sha); pdata[0] = (void*)1; printf("Init."); return RC_NOHEADERS + RC_STREAMING; // don't build headers automatically } } } else { // websocket connection here const unsigned char websocketTerm[2] = { 0x00, 0xFF }; // websocket close = opcode 0x8 printf("Streaming!\n"); // TODO: next find way to get next user input (best would be to only wake up on user input or if we have something to send?) char *buf = alloca(2); buf[0] = 0; buf[1] = 0; pdata[0]++; if ((int)(pdata[0]) &gt;= 20) { xbuf_ncat(reply, (char *)websocketTerm, 2); printf("Fin.\n"); pdata[0] = 0; // cleanup return RC_NOHEADERS; } return RC_NOHEADERS + RC_STREAMING; } xbuf_cat(reply, "test"); return 403; </code></pre>
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