Graphviz with HTML-like nodes, trying to control arrow shape - graphviz

Question

I'm trying to create a representation of haproxy redirects and also linking to services behind the haproxy.
I've got the following dot code:
digraph structs {
node [shape=plaintext]
subgraph cluster_haproxy {
label = "haproxy";
haproxy [label=<
<TABLE BORDER="3" CELLBORDER="1" CELLSPACING="50">
<TR>
<TD PORT="80">80</TD>
<TD PORT="443">443</TD>
</TR>
</TABLE>
>];
}
subgraph cluster_service001 {
label = "service001";
service001 [label=<
<TABLE BORDER="3" CELLBORDER="1" CELLSPACING="4">
<TR>
<TD PORT="123456789">123456789</TD>
</TR>
</TABLE>
>];
}
haproxy:80:e -> haproxy:443:w;
haproxy:443 -> service001:123456789;
}
Which results in this image, showing that port 80 gets redirected to port 443:
What I'm looking to achieve is just a straight arrow from 80 to 443, without any curve.
Do note that there may well be more ports on that same line.
I tried adding splines=line
I tried it with record-based nodes, giving them a rank=same to keep them next to each other, but that gives me this error message:
Warning: flat edge between adjacent nodes one of which has a record
shape - replace records with HTML-like labels
I tried it with box shape, but that put the items in the wrong order left to right.
Running out of ideas here. Any suggestions for how to properly do something like this would very much be appreciated.

Answer 1

GraphViz do not handle internal edges in nodes vell
I suggest you switch to 2 levels of clusters instead like here:
digraph structs {
node [shape=plaintext]
subgraph cluster_haproxy {
label = "haproxy";
subgraph cluster_haproxy2 {
penwidth=3
label=""
node[shape=rect]
{rank=same
80
443}
}
}
subgraph cluster_service001 {
label = "service001";
subgraph cluster_service001 {
penwidth=3
label=""
123456789[shape=rect]
}
}
80 -> 443
443 -> 123456789
}