localhost vs LAN : speed difference?

Question

I'm currently in the process of performance profiling. We have a basic client/server application. Would the TCP transfer speed be different if I ran client/server on the same machine (localhost) vs across two computers on a LAN?

Answer 1

TCP transfer speed will be! because if you ran it on same computer it will forward packets locally without even touching LAN and network adapter.

But overall speed of client+server may be better on different machines, especially if you do not communicate with server too often.

Answer 2

When using localhost, local resources are more likely to be the performance bottleneck because of memory, disk, cpu, etc. When using two computers, its more likely the network will be the bottleneck because of latency, bandwidth, throughput, packet loss, etc.

It depends on what your application does and how it uses the network, client, and server.