Firefox cannot communicate securely error occurred

Hello,
I am using a server application that needs to communicate with clients through sockets but I get the following error message after an initial data exchange in the middle of the connection. The error message shows the communication security issues. How can I avoid this issue without having any trouble? Have any idea to remove this problem? I would be grateful to you. Thanks.

Alert
Firefox and www68.gu.edu.au cannot communicate security because they have no common encryption algorithms.
