Delphi - Communication over internet (behind router)

Hi Freelancers! Please, read all the information / requirements before place a bid. I already created a remote desktop application, using Delphi 7 and Synapse ([login to view URL]), that allow users to see/control a remote computer and transfer files/folders, but it works only on local network area (LAN). Now is been necessary it to work over internet (WAN), behind routers, just like "TeamViewer" does... I need you to create an example code / application, that can send a simple stream (file) from a computer to another, each one in different LAN areas (behind routers), over the internet, without the need to configure port forwarding, etc. In my researchs, I understood that there is more than one way for doing this job. I expect it to be done in the most efficient way, in order to not compromise much the transmission speed. I can buy some Delphi third party component / SDK licence to make things easier for you. For now, I prefer to use Synapse UDP protocol and Delphi 7. But if you already have something done with a different protocol or Delphi version, please let me know (I have Delphi XE4 and below licences). Please, see attached an ilustrating image. I need PC-01 to connect with PC-02 (same LAN) or PC-01 to connect with PC-03 (outside LAN). Thank you for your interest in this job!