TCP is the only widely supported protocol for reliable communication. Therefore, TCP is the obvious choice when developing distributed systems that need to work on a wide range of platforms. Also, for this to work a developer has to use the standard TCP interface provided by a given operating system.

This work explores various ways to use TCP in high performance distributed systems. More precisely, different ways to use the standard Unix TCP API efficiently are explored, but the findings apply to other operating systems as well. The main focus is how various threading models affect TCP input in a process that has to handle both computation and I/O.

The threading models have been evaluated in a cluster of Linux workstations and the results show that a model with one dedicated I/O thread generally is good. It is at most 10% slower than the best model in all tests, while the other models are between 30 to 194% slower in specific tests.