DWDS requests are sent to wrong port

Hi!

I'm running webdev with the following command: `cd dart_app & webdev serve web:7777 --hostname 0.0.0.0 --auto restart --tls-cert-chain=localhost.pem --tls-cert-key=localhost-key.pem`. I have a reverse proxy locally to redirect requests where the URL path starts with /a to port 7777 (it also removes the /a).

Proxy configuration

For some reason, requests made to /$dwdsSseHandler are being sent directly to port 7777 and the page doesn't load. I created a client-side workaround:

Workaround

index.html:
```html


```
dwds-redirect.js:
```js
// Redirect Dart Web Developer Service (DWDS) requests to port 5173.
(function () {
'use strict';

if (window.location.port !== '5173') {
return;
}

const TARGET_PORT = 5173;
const SSE_HANDLER_PATH = '/$dwdsSseHandler';

// Intercept fetch requests.
const originalFetch = window.fetch;
window.fetch = function (input, init) {
let url = typeof input === 'string' ? input : input.url;

if (url && url.includes(SSE_HANDLER_PATH)) {
try {
const urlObj = new URL(url, window.location.origin);
if (urlObj.pathname === SSE_HANDLER_PATH || urlObj.pathname.endsWith(SSE_HANDLER_PATH)) {
urlObj.port = TARGET_PORT;
urlObj.protocol = window.location.protocol;
url = urlObj.toString();

if (typeof input === 'string') {
input = url;
} else {
input = new Request(url, input);
}
}
} catch (e) {
console.warn('Failed to redirect SSE handler URL:', e);
}
}

return originalFetch.call(this, input, init);
};

// Intercept XMLHttpRequest.
const originalOpen = XMLHttpRequest.prototype.open;
XMLHttpRequest.prototype.open = function (method, url, async, user, password) {
if (url && url.includes(SSE_HANDLER_PATH)) {
try {
const urlObj = new URL(url, window.location.origin);
if (urlObj.pathname === SSE_HANDLER_PATH || urlObj.pathname.endsWith(SSE_HANDLER_PATH)) {
urlObj.port = TARGET_PORT;
urlObj.protocol = window.location.protocol;
url = urlObj.toString();
}
} catch (e) {
console.warn('Failed to redirect SSE handler URL:', e);
}
}

return originalOpen.call(this, method, url, async, user, password);
};

// Intercept EventSource (for SSE connections).
const originalEventSource = window.EventSource;
window.EventSource = function (url, eventSourceInitDict) {
if (url && url.includes(SSE_HANDLER_PATH)) {
try {
const urlObj = new URL(url, window.location.origin);
if (urlObj.pathname === SSE_HANDLER_PATH || urlObj.pathname.endsWith(SSE_HANDLER_PATH)) {
urlObj.port = TARGET_PORT;
urlObj.protocol = window.location.protocol;
url = urlObj.toString();
}
} catch (e) {
console.warn('Failed to redirect SSE handler URL:', e);
}
}

return new originalEventSource(url, eventSourceInitDict);
};

console.log('DWDS SSE handler redirect configured to port ' + TARGET_PORT + '.');
})();

```

Can DWDS make requests to the correct port? A possible implementation is to try a port and if the request fails try another port.

Ideally I would also want to remove the `--tls-cert-chain=localhost.pem --tls-cert-key=localhost-key.pem` flags from webdev, but doing so the page stays blank and doesn't load, although all network requests succeed.