How to perform an exchange between two highly loaded services if their number of connections is more than 65556?

Question

linux

There are two servers that exchange information using the http protocol. The fact is that the number of their connections can exceed more than 65556 (More than the number of ports for one ip). How can you increase the number of connections?
Two servers have fighting ip addresses

Answer 1

using the http protocol

There is no point in such a number of ports, switch to keep-alive (for example, zmq), and 1-10 ports will be enough to load the hardware / network at 100%

Answer 2

Add another network interface?
Add another IP to the same interface?
round-robin and spread the load across multiple machines.

Answer 3

In sysconfig, you can increase the number of active tcp connections and their lifetime.
net.netfilter.nf_conntrack_max = desired number
net.netfillter.nf_conntrack_tcp_timeout_established = 18000, for example.