cant able to connect with socket while using a custom port on particular domain

        I am having an issue while connecting to socket when i am using a custom port such as 9999 on my domain and my socket server is installed on nodejs, while using the link 197.699.989:999 then it works but when i am using the domain as https://mydomain.zyz:9999 then it doesn't work. On iOS apps i am getting an error as 

            column = 27057
            description = 404
            line = 1
            type = TransportError

        and on web apps i am getting an error as 

GET https://mydomain.zyz/socket.io/?EIO=3&transport=polling&t=Lnenm3s 404

via Piyush Ranjan Malviya