How do I debug error ECONNRESET in Node.js?

Question

You might have guessed it already: it's a connection error.

"ECONNRESET" means the other side of the TCP conversation abruptly closed its end of the connection. This is most probably due to one or more application protocol errors. You could look at the API server logs to see if it complains about something.

But since you are also looking for a way to check the error and potentially debug the problem, you should take a look at "How to debug a socket hang up error in NodeJS?" which was posted at stackoverflow in relation to an alike question.

Quick and dirty solution for development:

Use longjohn, you get long stack traces that will contain the async operations.

Clean and correct solution: Technically, in node, whenever you emit an 'error' event and no one listens to it, it will throw. To make it not throw, put a listener on it and handle it yourself. That way you can log the error with more information.

To have one listener for a group of calls you can use domains and also catch other errors on runtime. Make sure each async operation related to http(Server/Client) is in different domain context comparing to the other parts of the code, the domain will automatically listen to the error events and will propagate it to it's own handler. So you only listen to that handler and get the error data. You also get more information for free.

EDIT (2013-07-22)

As I wrote above:

"ECONNRESET" means the other side of the TCP conversation abruptly closed its end of the connection. This is most probably due to one or more application protocol errors. You could look at the API server logs to see if it complains about something.

What could also be the case: at random times, the other side is overloaded and simply kills the connection as a result. If that's the case, depends on what you're connecting to exactly…

But one thing's for sure: you indeed have a read error on your TCP connection which causes the exception. You can see that by looking at the error code you posted in your edit, which confirms it.

A simple tcp server I had for serving the flash policy file was causing this. I can now catch the error using a handler:

# serving the flash policy file
net = require("net")

net.createServer((socket) =>
  //just added
  socket.on("error", (err) =>
    console.log("Caught flash policy server socket error: ")
    console.log(err.stack)
  )

  socket.write("<?xml version=\"1.0\"?>\n")
  socket.write("<!DOCTYPE cross-domain-policy SYSTEM \"http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd\">\n")
  socket.write("<cross-domain-policy>\n")
  socket.write("<allow-access-from domain=\"*\" to-ports=\"*\"/>\n")
  socket.write("</cross-domain-policy>\n")
  socket.end()
).listen(843)

I had a similar problem where apps started erroring out after an upgrade of Node. I believe this can be traced back to Node release v0.9.10 this item:

• net: don't suppress ECONNRESET (Ben Noordhuis)

Previous versions wouldn't error out on interruptions from the client. A break in the connection from the client throws the error ECONNRESET in Node. I believe this is intended functionality for Node, so the fix (at least for me) was to handle the error, which I believe you did in unCaught exceptions. Although I handle it in the net.socket handler.

You can demonstrate this:

Make a simple socket server and get Node v0.9.9 and v0.9.10.

require('net')
    .createServer( function(socket) 
    {
           // no nothing
    })
    .listen(21, function()
     {
           console.log('Socket ON')
    })

Start it up using v0.9.9 and then attempt to FTP to this server. I'm using FTP and port 21 only because I'm on Windows and have an FTP client, but no telnet client handy.

Then from the client side, just break the connection. (I'm just doing Ctrl-C)

You should see NO ERROR when using Node v0.9.9, and ERROR when using Node v.0.9.10 and up.

In production, I use v.0.10. something and it still gives the error. Again, I think this is intended and the solution is to handle the error in your code.

Had the same problem today. After some research i found a very useful --abort-on-uncaught-exception node.js option. Not only it provides much more verbose and useful error stack trace, but also saves core file on application crash allowing further debug.

I was facing the same issue but I mitigated it by placing:

server.timeout = 0;

before server.listen. server is an HTTP server here. The default timeout is 2 minutes as per the API documentation.

I also get ECONNRESET error during my development, the way I solve it is by not using nodemon to start my server, just use "node server.js" to start my server fixed my problem.

It's weird, but it worked for me, now I never see the ECONNRESET error again.

Another possible case (but rare) could be if you have server to server communications and have set server.maxConnections to a very low value.

In node's core lib net.js it will call clientHandle.close() which will also cause error ECONNRESET:

if (self.maxConnections && self._connections >= self.maxConnections) {
  clientHandle.close(); // causes ECONNRESET on the other end
  return;
}