Mongoose Websocket Server with JavaScript Websocket Client? #1685

efweber999 · 2022-08-26T11:33:03Z

efweber999
Aug 26, 2022

Hi,

I have an application where I would like to use a Mongoose websocket server, but it needs to communicate with an existing JavaScript websocket client. I see that the way in which Mongoose upgrades to websocket is based on having "/websocket" in the uri. So the example websocket server does not connect to the existing JavaScript websocket client. I'm sure I can get around this, but my question before investing time is; is the rest of the websocket server code compliant with the websocket standard, or will communicating with the JavaScript client have additional issues?

Here is a simple version of the JavaScript websocket client. Many Thanks.

Index.html

<!DOCTYPE html>

<html lang="en">
 <head>
  <meta charset="utf-8" />

  <title>Simple Websocket Client</title>
  <meta name="description" content="Basic template" />
 </head>

 <body>
  <script src="/index.js"></script>
 </body>
</html>

index.js

alert("[message] Will now upgrade to websocket.");

var socket = new WebSocket('ws://localhost:9000');

socket.onopen = function(e) {
  alert("[open] Connection established");
  alert("Sending message to server");
  socket.send("The quick brown fox jumps over the lazy dog");
};

socket.onmessage = function(event) {
  alert(`[message] Data received from server: ${event.data}`);
};

socket.onclose = function(event) {
  if (event.wasClean) {
    alert(`[close] Connection closed cleanly, code=${event.code} reason=${event.reason}`);
  } else {
    alert('[close] Connection died');
  }
};

socket.onerror = function(error) {
  alert(`[error] ${error.message}`);
};

Answered by scaprile

Aug 26, 2022

RFC6455 section 3 clearly allows URI paths.
Observe the example code, you control your URIs, you decide where to upgrade. The choice of using /websocket is just a convenience to be able to also serve HTML using a single port (and a single listener). How do you plan to serve that client to the browser ?
If you don't want to serve HTML then just upgrade on any URI, just change

mongoose/examples/websocket-server/main.c

Lines 18 to 32 in 7252f53

     } else if (ev == MG_EV_HTTP_MSG) {  
   struct mg_http_message *hm = (struct mg_http_message *) ev_data;  
   if (mg_http_match_uri(hm, "/websocket")) {  
   // Upgrade to websocket. From now on, a connection is a full-duplex  
   // Webso…

View full answer

scaprile · 2022-08-26T12:08:09Z

scaprile
Aug 26, 2022
Collaborator

RFC6455 section 3 clearly allows URI paths.
Observe the example code, you control your URIs, you decide where to upgrade. The choice of using /websocket is just a convenience to be able to also serve HTML using a single port (and a single listener). How do you plan to serve that client to the browser ?
If you don't want to serve HTML then just upgrade on any URI, just change

mongoose/examples/websocket-server/main.c

Lines 18 to 32 in 7252f53

    
           } else if (ev == MG_EV_HTTP_MSG) { 
        
             struct mg_http_message *hm = (struct mg_http_message *) ev_data; 
        
             if (mg_http_match_uri(hm, "/websocket")) { 
        
               // Upgrade to websocket. From now on, a connection is a full-duplex 
        
               // Websocket connection, which will receive MG_EV_WS_MSG events. 
        
               mg_ws_upgrade(c, hm, NULL); 
        
             } else if (mg_http_match_uri(hm, "/rest")) { 
        
               // Serve REST response 
        
               mg_http_reply(c, 200, "", "{\"result\": %d}\n", 123); 
        
             } else { 
        
               // Serve static files 
        
               struct mg_http_serve_opts opts = {.root_dir = s_web_root}; 
        
               mg_http_serve_dir(c, ev_data, &opts); 
        
             } 
        
           } else if (ev == MG_EV_WS_MSG) {

to

} else if (ev == MG_EV_HTTP_MSG) {
    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
    mg_ws_upgrade(c, hm, NULL);
} else if (ev == MG_EV_WS_MSG) {

You might as well modify your JS client by adding /websocket after :9000
Otherwise, add another listener at port 9000 with its own event handler as the one above; you'll serve HTTP on port 8000 and WS on port 9000

3 replies

efweber999 Aug 26, 2022
Author

Thanks for the quick response!

Thanks also for clarification on the spec. I'm learning this, and I think I'm assuming it's more complicated than it actually is. Actually, I've looked at multiple websocket libraries and I think everyone makes it more complicated than Mongoose does.

I need to serve the HTML/Javascript to the client and then upgrade to websocket. So I'm going to add "/websocket" to ws://localhost:9000, and go from there.

Best

efweber999 Aug 26, 2022
Author

Using the stock websocket-server.c
That was easy. ;)

scaprile Aug 26, 2022
Collaborator

Mongoose is designed for ease of use

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	} else if (ev == MG_EV_HTTP_MSG) {
	struct mg_http_message hm = (struct mg_http_message ) ev_data;
	if (mg_http_match_uri(hm, "/websocket")) {
	// Upgrade to websocket. From now on, a connection is a full-duplex
	// Webso…

Mongoose Websocket Server with JavaScript Websocket Client? #1685

efweber999 Aug 26, 2022

Index.html

index.js

Replies: 1 comment · 3 replies

scaprile Aug 26, 2022 Collaborator

efweber999 Aug 26, 2022 Author

efweber999 Aug 26, 2022 Author

scaprile Aug 26, 2022 Collaborator

efweber999
Aug 26, 2022

Replies: 1 comment 3 replies

scaprile
Aug 26, 2022
Collaborator

efweber999 Aug 26, 2022
Author

efweber999 Aug 26, 2022
Author

scaprile Aug 26, 2022
Collaborator