I was trying to keep a socket connection alive from the google chrome's fetch API to a remote express server and found the request headers have to match Node.JS's native <net.socket> connection settings.
I set the headers object on my client-side script with the following options:
/* ----- */
head = new headers();
head.append("Connnection", "keep-alive")
head.append("Keep-Alive", `timeout=${1*60*5}`) //in seconds, not milliseconds
/* apply more definitions to the header */
fetch(url, {
method: 'OPTIONS',
credentials: "include",
body: JSON.stringify(data),
cors: 'cors',
headers: head, //could be object literal too
cache: 'default'
})
.then(response=>{
....
}).catch(err=>{...});
And on my express server I setup my router as follows:
router.head('absolute or regex', (request, response, next)=>{
req.setTimeout(1000*60*5, ()=>{
console.info("socket timed out");
});
console.info("Proceeding down the middleware chain link...\n\n");
next();
});
/*Keep the socket alive by enabling it on the server, with an optional
delay on the last packet sent
*/
server.on('connection', (socket)=>socket.setKeepAlive(true, 10))
WARNING
Please use common sense and make sure the users you're keeping the socket connection open to is validated and serialized. It works for Firefox as well, but it's really vulnerable if you keep the TCP connection open for longer than 5 minutes.
I'm not sure how some of the lesser known browsers operate, but I'll append to this answer with the Microsoft browser details as well.