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Version: 4.x

Behind a reverse proxy

You will find below the configuration needed for deploying a Socket.IO server behind a reverse-proxy solution, such as:

In a multi-server setup, please check the documentation here.

NginX​

Content of /etc/nginx/nginx.conf:

http {
  server {
    listen 80;

    location / {
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header Host $host;

      proxy_pass http://localhost:3000;

      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
    }
  }
}

Related:

If you only want to forward the Socket.IO requests (for example when NginX handles the static content):

http {
  server {
    listen 80;
    root /var/www/html;

    location /socket.io/ {
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header Host $host;

      proxy_pass http://localhost:3000;

      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
    }
  }
}

Or with a custom path:

http {
  server {
    listen 80;
    root /var/www/html;

    location /my-custom-path/ {
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header Host $host;

      proxy_pass http://localhost:3000;

      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
    }
  }
}

In that case, the server and the client must be configured accordingly:

Server

import { Server } from "socket.io";

const io = new Server({
  path: "/my-custom-path/"
});

Client

import { io } from "socket.io-client";

const socket = io({
  path: "/my-custom-path/"
});

Apache HTTPD​

Content of /usr/local/apache2/conf/httpd.conf:

Listen 80

ServerName example.com

LoadModule mpm_event_module             modules/mod_mpm_event.so

LoadModule authn_file_module            modules/mod_authn_file.so
LoadModule authn_core_module            modules/mod_authn_core.so
LoadModule authz_host_module            modules/mod_authz_host.so
LoadModule authz_groupfile_module       modules/mod_authz_groupfile.so
LoadModule authz_user_module            modules/mod_authz_user.so
LoadModule authz_core_module            modules/mod_authz_core.so

LoadModule headers_module               modules/mod_headers.so
LoadModule lbmethod_byrequests_module   modules/mod_lbmethod_byrequests.so
LoadModule proxy_module                 modules/mod_proxy.so
LoadModule proxy_balancer_module        modules/mod_proxy_balancer.so
LoadModule proxy_http_module            modules/mod_proxy_http.so
LoadModule proxy_wstunnel_module        modules/mod_proxy_wstunnel.so
LoadModule rewrite_module               modules/mod_rewrite.so
LoadModule slotmem_shm_module           modules/mod_slotmem_shm.so
LoadModule unixd_module                 modules/mod_unixd.so

User daemon
Group daemon

ProxyPass / http://localhost:3000/
RewriteEngine on
RewriteCond %{HTTP:Upgrade} websocket [NC]
RewriteCond %{HTTP:Connection} upgrade [NC]
RewriteRule ^/?(.*) "ws://localhost:3000/$1" [P,L]

# must be bigger than pingInterval (25s by default) + pingTimeout (20s by default)
ProxyTimeout 60

Related:

Node.js http-proxy​

Installation: npm i http-proxy

const httpProxy = require("http-proxy");

httpProxy
  .createProxyServer({
    target: "http://localhost:3000",
    ws: true,
  })
  .listen(80);

Documentation

Caddy 2​

Content of Caddyfile for Caddy 2, if you only want to forward the Socket.IO requests

example.com {
    reverse_proxy /socket.io/* localhost:3000
}

Or, if you want a custom path:

example.com {
  rewrite /path /path/
  handle_path /path/* {
    rewrite * /socket.io{path}
    reverse_proxy localhost:3000
  }
}

Related