If you receive an error message stating the connection to the server was lost or refused, then the problem is probably that the client is unable to communicate with the server. Check that you are using the correct server address and the correct port number. Ensure the server is running on the specified computer. Ensure the port is not blocked by a firewall. Ensure that you have the necessary Internet or network connection to connect to the server. Ensure that any antivirus software is not blocking the connection.