Enable HTTPS/secure WebSocket connections

[tim-we]

• Find out what it takes to enable secure connections on the server (the client changes for this are trivial)
• Is there a noticeable performance hit when using wss:// instead of ws:// ?
• remove client error dialog & check (currently shows message asking the user to switch to HTTP)

[tim-we]

• https://github.com/jetty-project/embedded-jetty-cookbook/blob/jetty-9.4.x/src/main/java/org/eclipse/jetty/cookbook/websocket/SecureWebSocketServer.java
• https://stackoverflow.com/a/38026079/3315770
• https://stackoverflow.com/questions/57164319/jetty-server-with-https

[tim-we]

We will need a certificate for the Websocket server, so it's probably a good idea to use a domain instead of the raw IP (like we do at the moment). I created ws.ringofsnakes.io for this.

[tim-we]

Test URL: https://ringofsnakes.io/?useSSL

The connection does not work unfortunately though I do not know why. In Azure I added a rule to allow inbound TCP connections on port 443 (Settings > Networking > Inbound port rules) and on the server I forwarded those to port 8443 (sudo iptables -A PREROUTING -t nat -p tcp --dport 443 -j REDIRECT --to-ports 8443). I also imported the certificate I got from ionos with keytool: keytool -importcert -file ssl_cert.cert.

Connecting manually to https://ws.ringofsnakes.io/game I get an SSL_ERROR_HANDSHAKE_FAILURE_ALERT error.

[tim-we]

Finally got this working thanks to: https://stackoverflow.com/a/65459423/3315770