This question has been asked previously but not recently and not with a clear answer.
Using Socket.io, is there a maximum number of concurrent connections that one can maintain before you need to add another server?
Does anyone know of any active production environments that are using websockets (particularly socket.io) on a massive scale? I'd really like to know what sort of setup is best for maximum connections?
Because Websockets are built on top of TCP, my understanding is that unless ports are shared between connections you are going to be bound by the 64K port limit. But I've also seen reports of 512K connections using Gretty. So I don't know.
After making configurations, you can check by writing this command on terminal
sysctl -a | grep file
This guy appears to have succeeded in having over 1 million concurrent connections on a single Node.js server.
http://blog.caustik.com/2012/08/19/node-js-w1m-concurrent-connections/
It's not clear to me exactly how many ports he was using though.
For +300k concurrent connection:
Set these variables in /etc/sysctl.conf:
fs.file-max = 10000000
fs.nr_open = 10000000
Also, change these variables in /etc/security/limits.conf:
* soft nofile 10000000
* hard nofile 10000000
root soft nofile 10000000
root hard nofile 10000000
And finally, increase TCP buffers in /etc/sysctl.conf, too:
net.ipv4.tcp_mem = 786432 1697152 1945728
net.ipv4.tcp_rmem = 4096 4096 16777216
net.ipv4.tcp_wmem = 4096 4096 16777216
for more information please refer to this.
I tried to use socket.io on AWS, I can at most keep around 600 connections stable.
And I found out it is because socket.io used long polling first and upgraded to websocket later.
after I set the config to use websocket only, I can keep around 9000 connections.
Set this config at client side:
const socket = require('socket.io-client')
const conn = socket(host, { upgrade: false, transports: ['websocket'] })
Source: Stackoverflow.com