# Networking: netstat -s: 1523 times the listen queue of a socket overflowed — accept queue full, connections dropped

**Code:** `times the listen queue of a socket overflowed` · **Category:** Networking · **Seen on:** Linux, Networking

The application accepts connections slower than they arrive, so the kernel's accept queue overflows.

## Meaning

Backlog is capped by `min(listen backlog, net.core.somaxconn)`. Raise `somaxconn` and the backlog in the app/server (nginx `listen ... backlog=`, Node `server.listen(port, host, backlog)`), and fix whatever makes the app slow to `accept()` (blocked event loop, too few workers).

## Common causes

- Low `somaxconn` / application backlog
- App too slow to accept (blocked event loop/workers)
- Traffic bursts
- Single-process server saturated
- Default 128/511 backlog on a busy host

## Quick fix

1. Check: `nstat -az TcpExtListenOverflows`
2. Raise `net.core.somaxconn` and the app backlog
3. Add workers and unblock the accept loop

## Detailed fix by platform

### Linux

1. 

```bash
nstat -az TcpExtListenOverflows TcpExtListenDrops
sudo sysctl -w net.core.somaxconn=4096
```


## How to diagnose

1. **ListenOverflows** — Rising?
2. **Backlog** — Large enough?
3. **App** — Accepting promptly?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/networking/listen-queue-overflowed-somaxconn)