In OpenFlow-based software-defined network, we need two modules called OpenFlow datapath and controller (e.g. NOX). More specifically, in a commuter (OpenFlow-enabled switch/router) we need to start two daemons called ofdatapath and ofprotocol. The former is the datapath functioning itself and the latter, is an auxiliary module that is used to connect ofdataptah to an OpenFlow controller. Look this example:
Controller: ./nox_core -i ptcp:6633 switch Datapath: ./ofdatapath -i eth0.1,eth0.2,eth0.3,eth0.4 -d 000000000001 --no-slicing punix:/var/run/sock ./ofprotocol unix:/var/run/sock tcp:192.168.1.10:6633
The parameter unix:/var/run/sock and tcp:192.168.1.10:6633 of ofprotocol are used to create a local connection to ofdatapath and a remote connection to NOX controller. That’s all.