JavaScript

Socket Hang Up: What It Means and How to Fix It

Error reference

Socket Hang Up

Language

JavaScript

Severity

High

When it happens

The 'socket hang up' error occurs in Node.js when an HTTP connection is closed by the server before a complete response is received.

Potential fixes

Always attach an 'error' event handler to Node.js HTTP requests. Implement retry logic for idempotent requests. Check server-side logs to determine why the connection is being closed early. Increase proxy timeout settings if the server needs more processing time.

Deep dive

The 'socket hang up' error occurs in Node.js when an HTTP connection is closed by the server before a complete response is received. It is closely related to ECONNRESET and typically means the server closed the socket prematurely.

Why it happens

•The server closes the connection before finishing the response body.
•A reverse proxy (nginx, load balancer) times out and terminates the connection.
•The server crashes while processing the request.
•Not draining the request body on the server side causes the client to time out.

Potential fixes

Always attach an 'error' event handler to Node.js HTTP requests. Implement retry logic for idempotent requests. Check server-side logs to determine why the connection is being closed early. Increase proxy timeout settings if the server needs more processing time.

Examples

JavaScript

Code that triggers the error

const http = require("http");
const req = http.get("http://example.com/api", (res) => {
  res.resume();
});
req.end();
// Server closes connection before sending full response

Error output

Error: socket hang up
    code: 'ECONNRESET'

Fixed code

const http = require("http");
const req = http.get("http://example.com/api", (res) => {
  let body = "";
  res.on("data", (chunk) => { body += chunk; });
  res.on("end", () => console.log(body));
});
req.on("error", (err) => {
  console.error("Request failed:", err.message);
});

Practice in English

How would you explain a Socket Hang Up to a fellow dev? Choose the right phrase:

"I hit an error...

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