When running a local web server for web app development, logs show that something is trying to GET /socket.io from localhost on port 3000. This happens when using puma inside a Docker container for a Rails app, as well as when using a simple local server with node. The traffic appears to be coming from somewhere, but it’s not clear where.

Rebooting the machine temporarily stops the traffic, but it eventually starts again. Background apps have been checked and it’s not coming from them. This issue does not occur on a similar laptop. It is unclear what is causing the traffic and what else can be done to find the source.


In the Rails app log:

Started GET "/socket.io/?X_LOCAL_SECURITY_COOKIE=&EIO=3&transport=polling&t=1560455293858-21046" for at 2019-06-13 19:48:13 +0000
ActionController::RoutingError (No route matches [GET] "/socket.io"):

In a simple node http-server one-pager:

[Thu Jun 13 2019 16:15:44 GMT-0400 (Eastern Daylight Time)] "GET /socket.io/?X_LOCAL_SECURITY_COOKIE=&EIO=3&transport=polling&t=1560456944267-21720" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.30 Safari/537.36 NVIDIACEFClient/rel_03_17/c6b7277 NVIDIAOSCClient/"
[Thu Jun 13 2019 16:15:44 GMT-0400 (Eastern Daylight Time)] "GET /socket.io/?X_LOCAL_SECURITY_COOKIE=&EIO=3&transport=polling&t=1560456944267-21720" Error (404): "Not found"

Clearly, there’s something running on the machine that is doing this, but I can’t find it. What else can I do to try and figure out where it’s coming from?

Askify Moderator Edited question May 5, 2023