Problem - client can't connect to socket.io service through nginx. Also i use socket.io namespaces like /plst_upds.

nginx conf:
resolver 127.0.0.11 valid=5s;

server {

listen 80;

server_name $DOMAIN;

client_header_timeout 120s;

client_body_timeout 120s;

send_timeout 120s;

root /usr/share/nginx/html;

index index.html;

location / {

try_files $uri $uri/ /index.html;

}

location /socket.io/ {

proxy_pass http://socket-service.railway.internal:8000/socket.io

proxy_http_version 1.1;

proxy_set_header Upgrade $http_upgrade;

proxy_set_header Connection "upgrade";

proxy_read_timeout 86400s;

proxy_send_timeout 86400s;

proxy_set_header Host $host;

proxy_set_header X-Real-IP $remote_addr;

proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

proxy_set_header X-Forwarded-Proto $scheme;

}

}

Server side:

sio = socketio.AsyncServer(

    async_mode="asgi",

    cors_allowed_origins=[

        "*",

    ],

)

app = socketio.ASGIApp(sio)
uvicorn.run(

    "main:app",

    host=settings.SELF_HOST, # "::"

    port=settings.SELF_PORT, # "8000"

    log_level=settings.SELF_LOG_LEVEL.lower(),

    reload=settings.SELF_RELOAD,

    )

Client side:

export const plst_upds_socket = io(

  'https://proj.up.railway.app' + '/plst_upds',

  {

    withCredentials: true,

  },

Logs nginx:

100.64.0.2 - - [13/Oct/2025:11:17:38 +0000] "POST /socket.io/?EIO=4&transport=polling&t=1h38ihkt&sid=cejHGsjkNSe44YlsAADq HTTP/1.1" 400 75 "https://proj.up.railway.app/dashboard" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:143.0) Gecko/20100101 Firefox/143.0" "91.195.184.192"

100.64.0.2 - - [13/Oct/2025:11:17:38 +0000] "POST /socket.io/?EIO=4&transport=polling&t=1h3afcth&sid=cejHGsjkNSe44YlsAADq HTTP/1.1" 400 75 "https://proj.up.railway.app/dashboard" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:143.0) Gecko/20100101 Firefox/143.0" "91.195.184.192"

100.64.0.3 - - [13/Oct/2025:11:17:38 +0000] "GET /socket.io/?EIO=4&transport=websocket&sid=cejHGsjkNSe44YlsAADq HTTP/1.1" 403 0 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:143.0) Gecko/20100101 Firefox/143.0" "91.195.184.192"

Logs server:

INFO: fd12:225a:8c4b:0:1000:70:c928:74c4:51088 - "GET /socket.io?EIO=4&transport=polling&t=1h36irkr HTTP/1.1" 200 OK

INFO: fd12:225a:8c4b:0:1000:70:c928:74c4:51092 - "POST /socket.io?EIO=4&transport=polling&t=1h38ihkt&sid=cejHGsjkNSe44YlsAADq HTTP/1.1" 400 Bad Request

INFO: fd12:225a:8c4b:0:1000:70:c928:74c4:51112 - "POST /socket.io?EIO=4&transport=polling&t=1h3afcth&sid=cejHGsjkNSe44YlsAADq HTTP/1.1" 400 Bad Request

INFO: fd12:225a:8c4b:0:1000:70:c928:74c4:51122 - "WebSocket /socket.io?EIO=4&transport=websocket&sid=cejHGsjkNSe44YlsAADq" 403

I don't know how it fixes. I need help...