start ros node without a launch file

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I would like to init and start a ros node as a service in an other framework to offer my data to an already existing data analysis software written in ROS. That means that this node is created within a non-ros process without a call of launch files.

So far I managed to call ros::init and create a nodeHandle etc. But I need to start any of rosnode first via roslaunch before my process get fully initialize (otherwise my process is blocked and waits for ROS). I guess roscore etc is missing.

How can I initialize all that within my own process, so that ROS gets fully set up without any call of roslaunch.