How to fix 'events.js :167 error Error: connect ECONNREFUSED 127.0.0.1:443' in Node.js when no other apps seems to be attempting to use the port? - node.js

Question

I'm getting the error described below when running my node.js app after perfoming a few api calls.
The error does not always show in the exactly same place/line of code. But most of the times it is at the end of the api call.
events.js:167
throw er; // Unhandled 'error' event
^
Error: connect ECONNREFUSED 127.0.0.1:443
at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1113:14)
Emitted 'error' event at:
at TLSSocket.socketErrorListener (_http_client.js:391:9)
at TLSSocket.emit (events.js:182:13)
at emitErrorNT (internal/streams/destroy.js:82:8)
at emitErrorAndCloseNT (internal/streams/destroy.js:50:3)
at process._tickCallback (internal/process/next_tick.js:63:19)
Based on similar questions here at SO my hypothesis is that a) there is something using 127.0.0.1:443 and therefore conflicting with my app or b) node is trying to use 127.0.0.1:443 but there is nothing there for it to use (my app is listening to localhost :3000).
Hyphothesis a) doesn't seem likely since after running netstat -ano | findstr 127.0.0.1:443 nothing shows up (when app is running and right after it terminates).
Also killed every node.exe and mongod.exeb using any port in my computer, closed the terminal and restarted the node app without success.
In case error is related with hypothesis b) I'm not sure how to address it.
api.post('/parsePOpdf', wagner.invoke(function(Pdfeq, Pdfdocspec, Product, User, Order){
return async function(req,res){
//... some code
pdfParser.on("pdfParser_dataError", errData => console.error(errData.parserError) );
pdfParser.on("pdfParser_dataReady", async function(pdfData) {
fs.writeFile("./test.json", JSON.stringify(pdfData), function(err){
console.log(err);
});
let pages = pdfData.formImage.Pages;
//console.log('pages 557', pages);
let order = {
orderDetails : {
supplier : [{
item : []
}]
}
};
for (const page of pages){
let value = await getItemsInPDF(page, productKeys, pdfParsingDetails, order, Product, customer, supplierLink, User);
//... more code
order = value;
}
return res.json(order);
});
pdfParser.loadPDF(pdfFile);
}
}));
I would expect the code to finish without throwing this error.

Answer 1

It turns out that the problem was in the api code: an http.get line to fetch a remote file was generating the conflict. This makes sense since the error was not present for other endpoints of the api.
So learning is that if the terminal reports no app using the suspected conflicting port (see question) answser should be within the same code and you need to go line by line to identify which one is causing the problem (instead of focusing on other apps trying to use the same port, like I was focusing on).