Web server refuses connections although max socket connections not exceeded (IDFGH-8004)

[mbratch]

I am using ESP-IDF v4.4.1 on an ESP32-Pico Kit v4.1.

My application has a REST API server which has been working well. I wanted to add a WebSocket interface, using the ESP32 as a WebSocket server, so I added a handler for it, in addition to my REST API path handlers.

    const httpd_uri_t httpdUri = {
        .uri = "/ws",
        .method = HTTP_GET,
        .handler = wsStart,
        .user_ctx = nullptr,
        .is_websocket = true
    };
    
    httpd_register_uri_handler(_server, &httpdUri);

Here's the handler function:

esp_err_t WebServer::wsStart(httpd_req_t *req)
{
    auto& status = Status::instance();
    auto& webServer = WebServer::instance();

    status.logf(Status::logInfo, "Starting websocket, handle = %d, fd = %d", req->handle, httpd_req_to_sockfd(req));

    webServer.wsSetHandle(req->handle);

    esp_err_t rc = webServer.wsSetFd(httpd_req_to_sockfd(req));

    if (rc == ESP_FAIL)
        status.log(Status::logError, "Too many websocket handles allocated");

    return rc;
}

In the javascript client, when the page is loaded, I open the WebSocket:

	let webSocket = new WebSocket(`ws://${location.host}/ws`);

	webSocket.onopen = function() {
		console.log('Websocket to BD-OTP open')
	}

	webSocket.onmessage = function(event) {
	    const output = JSON.parse(event.data)
            // Update DOM element based upon data
	}
	
	webSocket.onclose = function() {
		console.log('Websocket to BD-OTP closed')
		webSocket = null
	}

	webSocket.onerror = function(event) {
		console.log(`WebSocket ERROR: ${JSON.stringify(event, null, 4)}`);
	}

The WebSocket is basically working, but here's the problem: if I reload the page a number of times, the server soon stops responding. I have my maximum sockets set to 16 in my SDK config (which limits the actual number to 13 sockets in the code). But I do not have 13 sockets open, at least not based upon what I'm seeing. The following log is generated using handlers for the open_fn and close_fn events for the server:

I (25521) BD-OTB: Open socket hd = 1073549484, fd = 51
I (25541) BD-OTB: Open socket hd = 1073549484, fd = 52
I (25631) BD-OTB: Open socket hd = 1073549484, fd = 53
I (25726) BD-OTB: Open socket hd = 1073549484, fd = 54
I (25736) BD-OTB: Starting websocket, handle = 1073549484, fd = 54
I (37206) BD-OTB: Close socket hd = 1073549484, fd = 54
I (37386) BD-OTB: Open socket hd = 1073549484, fd = 55
I (37401) BD-OTB: Starting websocket, handle = 1073549484, fd = 55
I (47751) BD-OTB: Close socket hd = 1073549484, fd = 55
I (47976) BD-OTB: Open socket hd = 1073549484, fd = 56
I (47991) BD-OTB: Starting websocket, handle = 1073549484, fd = 56
I (50201) BD-OTB: Close socket hd = 1073549484, fd = 56
I (50371) BD-OTB: Open socket hd = 1073549484, fd = 57
I (50381) BD-OTB: Starting websocket, handle = 1073549484, fd = 57
I (50386) BD-OTB: Open socket hd = 1073549484, fd = 58
I (51231) BD-OTB: Close socket hd = 1073549484, fd = 57
I (51411) BD-OTB: Open socket hd = 1073549484, fd = 59
I (51421) BD-OTB: Starting websocket, handle = 1073549484, fd = 59
I (52051) BD-OTB: Close socket hd = 1073549484, fd = 59
I (52231) BD-OTB: Open socket hd = 1073549484, fd = 60
I (52241) BD-OTB: Starting websocket, handle = 1073549484, fd = 60
I (57896) BD-OTB: Close socket hd = 1073549484, fd = 60
I (58091) BD-OTB: Open socket hd = 1073549484, fd = 61
I (58101) BD-OTB: Starting websocket, handle = 1073549484, fd = 61
I (58811) BD-OTB: Close socket hd = 1073549484, fd = 61
I (58986) BD-OTB: Open socket hd = 1073549484, fd = 62
I (58996) BD-OTB: Starting websocket, handle = 1073549484, fd = 62
I (59626) BD-OTB: Close socket hd = 1073549484, fd = 62
I (59826) BD-OTB: Open socket hd = 1073549484, fd = 63
I (59836) BD-OTB: Starting websocket, handle = 1073549484, fd = 63
I (60451) BD-OTB: Close socket hd = 1073549484, fd = 63
W (60641) httpd: httpd_accept_conn: error in accept (23)
W (60641) httpd: httpd_server: error accepting new connection
W (61361) httpd: httpd_accept_conn: error in accept (23)
W (61361) httpd: httpd_server: error accepting new connection
W (62261) httpd: httpd_accept_conn: error in accept (23)
W (62266) httpd: httpd_server: error accepting new connection

From this log, when the client page is initially loaded, several sockets are opened, including the websocket. Each subsequent reload of the page generally closes the prior WebSocket and opens one new one in its place. I don't see a net gain in open sockets here. Nonetheless, after a few reloads, the ESP32 server stops responding and won't accept any more connections. This problem gets worst and happens much sooner if I add support for more WebSocket clients. In order to remedy this issue, I have to reboot the ESP32. Waiting for sockets to timeout and close does not resolve the issue.

[ESP-YJM]

Hi @mbratch , i think you can find the solution in #9395.

[mbratch]

@ESP-YJM thank you! I tried that and it appears to be working properly now after some brief testing.

[chipweinberger]

@ESP-YJM, IMO httpd_config_t.so_linger = false should be added & the default behavior =)

[ESP-YJM]

@chipweinberger Yes, that's a good idea. Add so_linger config can make sense.

[chipweinberger]

Great to see that merged, @ESP-YJM!

Is there a reason we don't care about the return value of setsockop? Please see my comment: #9395 (comment)