Java program without forward port in router

Question

I made application with java using socket. My computer is the server and my phone(android ) is the client. Only what i trying to do is to forward String from phone to client PC.

Everything works fine when i configure my router and open the port i using. i don't want every time when costumer will install my application will need to open port in the router.

I thought about using remote server that will run my server code. but i didn't find server that can do that . i don't want to make my pc a server for all costumers.

How does all the chats companies do it without open port?

Answer 1

You must look into UPnP. This is what /most/ if not /all/ torrent clients use to allow foreign connections, without forwarding ports. How chat clients do it is a different scenario. They use hacks such as firewall hole-punching using UDP (with an external server) http://www.h-online.com/security/features/How-Skype-Co-get-round-firewalls-747197.html see this link for details on UDP hole punching.

Also see this article http://www.codeproject.com/Articles/13285/Using-UPnP-for-Programmatic-Port-Forwardings-and-N for usage of UPnP. But this is in C++, but I think you will understand.

EDIT: http://4thline.org/projects/cling/ I found this. I think it can help you.