Graphviz - how to create a roundtrip stream

Question

I am trying to create a graph "round trip" using graphviz. Given the result below, my goal is to have PINK squares between NET and COM (note in the figure below that they are shifted to the right after NET).

• COM should be the first node on LEFT.

dot code:

digraph { 
rankdir = LR;
graph [fontname = "helvetica" ];
node [fontname = "helvetica"];
edge [fontname = "helvetica"];

COM [shape = circle, fillcolor = yellow, style = filled];
NET [shape = circle, fillcolor = yellow, style = filled];

fn1 [shape = BOX, fillcolor = green, style = filled, label = "PORT006"];
clazz1 [shape = BOX, fillcolor = red, style = filled, label = "O"];
ddate1 [shape = BOX, fillcolor = red, style = filled, label = "21-Apr-13"];
status1 [shape = BOX, fillcolor = red, style = filled, label = "OJ3COM6M"];

clazz1exch [shape = BOX, fillcolor = green, style = filled, label = "G"];
ddate1exch [shape = BOX, fillcolor = green, style = filled, label = "13-May-13"];   
status1exch [shape = BOX, fillcolor = green, style = filled, label = "GJ3COM6M"];

fn2 [shape = BOX, fillcolor = pink, style = filled, label = "PORT005"];
rbd2 [shape = BOX, fillcolor = pink, style = filled, label = "O"];
ddate2 [shape = BOX, fillcolor = pink, style = filled, label = "29-Apr-13"];
fare2 [shape = BOX, fillcolor = pink, style = filled, label = "OJ3COM6M"];

{ rank=same; clazz1 -> clazz1exch; }
{ rank= same; ddate1 -> ddate1exch; }
{ rank=same; status1 -> status1exch; }

 COM -> fn1 -> clazz1exch -> ddate1exch -> status1exch -> NET;
 NET -> fn2 -> rbd2 -> ddate2 -> fare2 -> COM;

 }

Answer 1

If you just change the direction of the edges back ( dir=back) by changing the line

NET -> fn2 -> rbd2 -> ddate2 -> fare2 -> COM;

in

edge[dir=back];
COM -> fare2 -> ddate2 -> rbd2 -> fn2 -> NET;

you should get: