The code for tspn.jl is explained in my blog article on opensourc.es
To run it you have to download Julia and install JuMP, Juniper, Ipopt and Distances.
You can use
] add JuMP
] add Junipper
] add Ipopt
] add Distances
include("tspn.jl")
solve_tspn(;file_name="tspn_25", relax=false)
I visualized the problem using d3.