CODEWITHSUNDEEP
tcpnetwork-programmingconnection
Dariusz
Dariusz

Reputation: 22241

How to initiate direct connection between clients connected to a server

Suppose that I have a server and the clients are connected to the server. The server is accessible through a public ip.

I would like to "forward" the connection so that the clients would be directly connected to each other withouth the server in the middle.

I do not know if this is possible at all and I myself couldn't find a way to do it.

Other assumptions:

I am looking for a strictly software solution, without the need to reconfigure router, open ports, etc. etc.

The reason I would like to achieve this is to reduce the load on server. Once a two clients are associated together there is no real need (except technical one) to continue using the server as a, sort of, proxy. Direct client connection would also reduce the latency of the connection.

Upvotes: 7

Views: 2329

Answers (4)

learner
learner

Reputation: 1982

You can do two things one is hole punching http://en.wikipedia.org/wiki/TCP_hole_punching so this will allow you to respond to your client who are behind NAT (you can configure your client to send their private ip and port number used by NAT to reply to them).

Other thing you can do is to make a peer-to-peer network as done by skype and make one of the client as relay network and keep track of active relay's and update them periodically. (see http://en.wikipedia.org/wiki/Skype_protocol )

So now your server has to just act as proxy and as an admin which kind of manage all connection but least amount of info pass through it.

I hope this help.

Upvotes: 2

LtWorf
LtWorf

Reputation: 7598

Some home routers support upnp and can be instructed to open a certain port and forward it to a certain client on the LAN.

You can use upnpc on GNU/Linux to open ports on the router. It also has a library to do it from C code (but it's not very well documented).

However this method might not work on all home devices, so in that case see the other answers.

Upvotes: 1

Mert
Mert

Reputation: 6065

A short answer is: it is not possible.

One of the main problems is that router do not know where to redirect the request from the server (or other client). Just a case : You have a router which has multiple devices(computer, cell phone...) behind it. It gets a request and do not know, who wants to get the request.

There is a workaround for that but it is not reliable (Does not work always.) Some Companies use it if it is possible, but they have always an alternative to that (like communication over server) if it fails. It is called nat punching. More details here: http://en.wikipedia.org/wiki/TCP_hole_punching

I do not know for which reason do you need. If you need it for client server connection you can use something like long polling, call back....

Otherwise you need to set the router, or take the route over the server.

Upvotes: 3

user1676075
user1676075

Reputation: 3086

Take a look at http://en.wikipedia.org/wiki/UDP_hole_punching. If neither machine has a public IP, and you can't open ports, and you don't want all data to pass through the server, this is probably the only other potential option. If this wouldn't work for you, you're likely stuck with all data going through the server. If you can set up port forwarding, that would make for a better solution, then just use the server to exchange IP and port information (as it exists at the time the connection is established).

Upvotes: 4

Related Questions