c++ - exchange data with socket.io server from embedded system websockets cpp client -

i'm unable exchange data socket.io server native c++ websocket (www.websocket.org) client. note not want solution based on boost i'm running websocket client embedded system (it has light-weight).

i've tried both lws_write_text , lws_write_http (no padding) modes. i'm not using secure sockets (i.e., not using wss or ssl certs).

myserver.js:

var io = require('socket.io').listen(80);  io.configure('production', function(){   io.enable('browser client etag');   io.set('log level', 3);   io.set('transports', ['websocket']); });  io.configure('development', function(){   io.set('log level', 3);   io.set('transports', ['websocket']); });  io.sockets.on('connection', function (socket) {   socket.emit('news', { hello: 'world' });   socket.on('my other event', function (data) {     console.log(data);   }); }); 

i've enhanced libwebsockets-test-echo.cpp sample code starting point , have working fine when both client , server use websockets c++ api. however, when connect socket.io server, server console reports: warn - unknown transport: "undefined" .

client.cpp:

...     struct per_session_data__echo {     // lws_write_text mode, pre_padding defined lws_send_buffer_pre_padding , post_padding lws_send_buffer_post_padding, otherwise they're both set 0.     unsigned char buf[pre_padding + 1400 + post_padding];     unsigned int len;     unsigned int index; };  static int callback_echo(struct libwebsocket_context *context,     struct libwebsocket *wsi,     enum libwebsocket_callback_reasons reason, void *user,     void *in, size_t len) {     struct per_session_data__echo *pss = (struct per_session_data__echo *)user;     int n;      switch (reason) {     case lws_callback_client_established:         lwsl_notice("client has connected\n");         pss->index = 0;         break;      case lws_callback_client_receive:         lwsl_notice("client rx: %s", (char *)in);         break;      case lws_callback_client_writeable:         /* send our packet... */         pss->len = sprintf((char *)&pss->buf[lws_send_buffer_pre_padding], "hello libwebsockets-test-echo client pid %d index %d\n", getpid(), pss->index++);         lwsl_notice("client tx: %s", &pss->buf[lws_send_buffer_pre_padding]);         n = libwebsocket_write(wsi, &pss->buf[lws_send_buffer_pre_padding], pss->len, lws_write_text);         if (n < 0) {             lwsl_err("error %d writing socket, hanging up\n", n);             return -1;         }         if (n < (int)pss->len) {             lwsl_err("partial write\n");             return -1;         }         break;     default:         break;     }      return 0; }  static struct libwebsocket_protocols protocols[] = {     /* first protocol must http handler */     {         "my other event",      /* name */         callback_echo,      /* callback */         sizeof(struct per_session_data__echo),  /* per_session_data_size */         0     },     {         null, null, 0, 0       /* end of list */     } };  ...  struct lws_context_creation_info info; info.port = context_port_no_listen; info.iface = "eth0"; info.gid = -1; info.uid = -1; info.options = 0; info.extensions = libwebsocket_get_internal_extensions(); info.protocols = protocols;  libwebsocket_context context_; context_ = libwebsocket_create_context(&info);  libwebsocket *wsi_; wsi_ = libwebsocket_client_connect(context_,     "localhost",     80, // port     0, // "ws:" (no ssl)     "/socket.io", // path     "localhost", // host name     "controller", // socket origin name     "my other event", // libwebsocket protocol name     -1     );  ... libwebsocket_callback_on_writable_all_protocol(&protocols_[0]);  ... int rc = 0; unsigned int oldus = 0; while (rc >= 0 && !forceexit_) {     struct timeval tv;      gettimeofday(&tv, null);      if (((unsigned int)tv.tv_usec - oldus) > pollingrate_) {         oldus = tv.tv_usec;     }     rc = libwebsocket_service(context_, 1000); // wait 1000 msec     if (rc != 0) printf("rc=%d\n", rc); } 

...

here's output 'sudo node server.js':

  info  - socket.io started   warn  - unknown transport: "undefined" 

here's output client.cpp console. not mislead "listening on port=0" it's context port setting used libwebsockets-test-echo.cpp, works websocket websocket client , server. note connection completes , output same both lws_write_text , lws_write_http modes.

listening on port=0 listening on interface=eth0 lwsts[12960]: initial logging level 7 lwsts[12960]: library version: 1.3 502b994 lwsts[12960]:  started daemon pid 0 lwsts[12960]:  static allocation: 4488 + (16 x 1024 fds) = 20872 bytes lwsts[12960]:  canonical_hostname = sogo lwsts[12960]: context->protocols[0].name='my other event' lwsts[12960]: lws_callback_openssl_load_extra_client_verify_certs lwsts[12960]: context->protocols[0].name='my other event' lwsts[12960]: lws_callback_protocol_init lwsts[12960]: websocketclient::connect(): connecting localhost:80 ... sslcerts=0 protocolnamelist='my other event' connecting address=localhost , port=80 lwsts[13340]: context->protocols[0].name='my other event' lwsts[13340]: lws_callback_add_poll_fd lwsts[13340]: context->protocols[0].name='my other event' lwsts[13340]: lws_callback_clear_mode_poll_fd lwsts[13340]: context->protocols[0].name='my other event' lwsts[13340]: lws_callback_client_confirm_extension_supported lwsts[13340]: context->protocols[0].name='my other event' lwsts[13340]: lws_callback_client_append_handshake_header lwsts[13340]: websocketclient::connect(): connected localhost:80 lwsts[13340]: context->protocols[0].name='my other event' lwsts[13340]: lws_callback_set_mode_poll_fd lwsts[13340]: websocketclient::run(): running ... lwsts[13340]: problems parsing header lwsts[13340]: context->protocols[0].name='my other event' lwsts[13340]: lws_callback_del_poll_fd