rails 5, NGINX Error during WebSocket handshake: Unexpected response code: 404 -

i try deploy simple web chat server (nginx/puma). receive error console of browser:

websocket connection 'ws://domain.com/cable' failed: error during websocket handshake: unexpected response code: 404 

my config server domain.conf:

upstream backend {   server unix:///var/run/backend.sock; }  server {   listen 80 ;   server_name domain.com;    root /home/rails/backend/public;   access_log /home/rails/backend/log/nginx.access.log;   error_log /home/rails/backend/log/nginx.error.log info;    try_files $uri/index.html $uri @backend;   location @backend {     proxy_set_header x-forwarded-for $proxy_add_x_forwarded_for;     proxy_set_header host $http_host;     proxy_redirect off;      proxy_pass http://backend;   }    location ^~ /assets/ {     gzip_static on;     expires max;     add_header cache-control public;   }    location /cable {         proxy_pass http://gifty;         proxy_http_version 1.1;         proxy_set_header upgrade $http_upgrade;         proxy_set_header connection "upgrade";       } } 

is wrong where? setup before. please me work out it