Distance from a point to the two neightbouring points (both directions) in on a polyline of a pipe system

I need to find the distance of a valve to the two neightbouring corners in a piping system.

I have the following shp files:
-Nodes for the valves
-Nodes for the corners
-line layer file of the piping system.

I need to compute the distance from a valve node, to the two neightbouring corners. So the search should be in both directions. I looked at options to make a network of the piping system and find the distance from the valve to the two nearest neightbours, but the problem is the direction restriction.

If one searches for the nearest two neightbours the result could be two corners at the one end of the pipe that were the closed, instead of one corner at one side of the pipe and the other corner at the other side of the pipe.

I added a picture to illustrate the problem. I should get the distances from the valve to corners 1 and 2. But with the nearest neightbour I would get the distance to corner 1 and 3.

Does anyone know how to deal with this problem?

Thank you very much!