Falló la conexión de WebSocket a :error durante el protocolo de enlace de WebSocket:código de respuesta inesperado:521

Este documento es para aquellos que usan el servidor echo laravel &nginx &socket.io &redis-server con un servidor separado entre el proyecto del cliente y el servidor redis.

1) Edite /etc/redis/redis.conf

bind 127.0.0.1
supervised no

Para

bind 0.0.0.0
supervised systemd

2) Actualice /etc/systemd/system/redis.service en [Service]

Type=notify
ExecStart=/usr/bin/redis-server /etc/redis/redis.conf  --supervised systemd

3) Nginx /etc/nginx/sites-enabled/reverse-proxy.conf

server {
  listen        443 ssl;
  listen        [::]:443 ssl;
  server_name   mysitecom;

  error_log     /var/log/nginx/proxy-error.log error;

  # Start the SSL configurations
  ssl                         on;
  ssl_certificate             /etc/nginx/certs/mysitecom.pem;
  ssl_certificate_key         /etc/nginx/certs/mysitecom.key;
  ssl_session_timeout         3m;
  ssl_session_cache           shared:SSL:50m;
  ssl_protocols               TLSv1.1 TLSv1.2;

  # Diffie Hellmann performance improvements
  ssl_ecdh_curve              secp384r1;

  location /socket.io {
    proxy_pass                          http://mysitecom:2096;
    proxy_http_version 1.1;
    proxy_set_header Upgrade            $http_upgrade;
    proxy_set_header Connection         "upgrade";
    proxy_set_header Host               $host;
    proxy_set_header X-Real-IP          $remote_addr;
    proxy_buffers 16 4k;
    proxy_buffer_size 2k;

    proxy_set_header X-Forwarded-For    $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto  https;
    proxy_set_header X-VerifiedViaNginx yes;
    proxy_read_timeout                  2h;
    proxy_connect_timeout               2h;
    proxy_redirect                      off;
  }
}

4) laravel-echo-server.json

{
    "authHost": "https://mysitecom",
    "authEndpoint": "/broadcasting/auth",
    "clients": [
        {
            "appId": "e45c056ec8ca8bd7",
            "key": "88d316b5cccafbc5e905aa9ee13e63f7"
        }
    ],
    "database": "redis",
    "databaseConfig": {
        "redis": {
            "host": "0.0.0.0",
            "port": "6379"
        },
        "sqlite": {
            "databasePath": "/database/laravel-echo-server.sqlite"
        }
    },
    "devMode": true,
    "host": null,
    "port": "2096",
    "protocol": "https",
    "socketio": {},
    "secureOptions": 67108864,
    "sslCertPath": "/etc/nginx/certs/mysitecom.pem",
    "sslKeyPath": "/etc/nginx/certs/mysitecom.key",
    "sslCertChainPath": "",
    "sslPassphrase": "",
    "subscribers": {
        "http": true,
        "redis": true
    },
    "apiOriginAllow": {
        "allowCors": true,
        "allowOrigin": "*",
        "allowMethods": "GET, POST",
        "allowHeaders": "Origin, Content-Type, X-Auth-Token, X-Requested-With, Accept, Authorization, X-CSRF-TOKEN, X-Socket-Id"
    }
}

Nota: para alguien que conecta DNS con cloudflare cambie el puerto predeterminado socket.io 6001 a lo siguiente aquí.