I'd re-write the existing VB.net code and translate it faithfully into C++ per specifications. I am assuming the protocol resembles (or is) one of: MTConnect, OPC, OMG DDS, or Woopsa; or some other protocol, which I would also assimilate in the course of the project.
After achieving a successful translation and testing of the equivalent C++ code, I would work closely with the engineer to improve the product.
Hard to say exactly how long it will take till I see more details, maybe 2 months or so.
I'm physically in Victoria, but I may be available for face-to-face meetings there as required. I've got some video clips from recent computer vision projects, and I can show you a doxygen C++ library API for a visual tracker if you'd like.