srpc/tools/templates/file/server.conf

{
  "server":
  {
    "port": 8080,
    "root": "./html/",
    "error_page" : [
      {
        "error" : [ 404 ],
        "page" : "404.html"
      },
      {
        "error" : [ 500, 502, 503, 504],
        "page" : "50x.html"
      }
    ]
  }
}