# lsof: can't identify protocol

DevFeed: [lsof: can't identify protocol](<https://devfeed.tech/articles/lsof-can-t-identify-protocol-38917.md>)

Original publisher: [Read original article](<https://idea.popcount.org/2012-12-09-lsof-cant-identify-protocol>)

Author: Marek

Published: 2012-12-08T23:00:00Z

Content type: article

Language: en

Sources: [Marek Majkowski](<https://devfeed.tech/sources/marek-majkowski.md>)

Topics: [WebSocket](<https://devfeed.tech/topics/websocket.md>), [Linux](<https://devfeed.tech/topics/linux.md>), [Library](<https://devfeed.tech/topics/library.md>), [debug](<https://devfeed.tech/topics/debug.md>)

Tags: [crash](<https://devfeed.tech/tags/crash.md>), [debug](<https://devfeed.tech/tags/debug.md>), [library](<https://devfeed.tech/tags/library.md>), [linux](<https://devfeed.tech/tags/linux.md>), [socket](<https://devfeed.tech/tags/socket.md>), [websockets](<https://devfeed.tech/tags/websockets.md>)

## AI overview

The article examines a SockJS-node issue in which enabling WebSockets appears to leak file descriptors and can lead to crashes. It reports that lsof handles the resulting half-closed sockets differently on FreeBSD and Linux, making the issue difficult to debug.

## Source excerpt

lsof: can't identify protocol SockJS-node users noticed that the server seems to be leaking file descriptors when websockets are enabled. The problem resulted in the usual crash. Additionally, was producing weird output, with line instead of a normal tcp/ip description. Where it should say something like: it said: The issue was hard to track, but eventually Yury Michurin found a culprit. It was a library which seems to be leaking sockets in state but didn't close them.