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Is there any way to overcome the router port forwarding on tcp/ip application

Meir Yan
Ranch Hand

Joined: Apr 27, 2006
Posts: 597
need to connect to computer over tcp/ip i have the external ip but without port forwarding I can't connect to the server . Is there any way to configure the server to accepts connection on the external ip and port define by the server without configuring the router ? (how does emule, FogCreek CoPilot, LogMeIn does it ? or other peer to peer application )
Henry Wong
author
Sheriff

Joined: Sep 28, 2004
Posts: 19070
    
  40

Meir Yan wrote:how does emule, FogCreek CoPilot, LogMeIn does it ? or other peer to peer application


Two possible answers...

1. They don't. In a peer to peer environment. It is not possible for two peers, both of which behind a router, to communicate. Only peers that can be reached can be connected to, so... if a peer is behind a router, the peer can't be reached. It must initiate the connections, and only to other peers that are reachable.

2. They use UPnP. Many routers should support a programmatic protocol to forward the port. The program connects to the router (which is generally its default gateway) and request that a port gets forwarded to it. The router doesn't have to be manually configured to forward the port, but needs to be configured to allow UPnP.

Henry


Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
Meir Yan
Ranch Hand

Joined: Apr 27, 2006
Posts: 597
thanks for the answer , can you please explain me what do you mean by
"... It must initiate the connections .."
in simple words can you explain the scenario?
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Is there any way to overcome the router port forwarding on tcp/ip application