Scale HAProxy for more than 64k websockets

If your 64k limit is due to source ports, you can do something like the following (a little hacky, but it was we currently do at SE for websockets (we have something like .5 million concurrent usually with HAProxy):

server ny-web01-1 10.0.0.1:8081 check
server ny-web01-2 10.0.0.1:8082 check
server ny-web01-3 10.0.0.1:8083 check

Also multiple instances is doable with keepalived. Just do something like round robin DNS over multiple IPs. Just ensure that the IPs always get picked up by active load balancers since DNS itself won't give you the load balancing (there are more options here as well, this one is just simple).