There is one unique connection per (address, port) pair.

huhtenberg · on Sept 23, 2011

Actually, the quintet of [protocol, src_ip, src_port, dst_ip, dst_port] is what's unique (protocol being TCP or UDP)

pacala · on Sept 23, 2011

Good point. Each unique client (address, port) can get a separate connection on a given/fixed server (address, port).

Rickasaurus · on Sept 23, 2011

Ahh I see, you just give one box a ton of IPs. Thanks :)

kornholi · on Sept 23, 2011

No, the pair uses the client IP which means the client can have as many connections to your server as number of ephemeral ports allowed. There is no limit on connections except ram AFAIK.

stonemetal · on Sept 23, 2011

Not sure why you got down voted, last time this topic came up the author was using EC2 instances for test clients, it took them 17 or so to get the number of connections to their server that they wanted. When the server IP, server port part of the 4 tuple is constant, it takes quite a few client IPs to turn 64K ports into a million.