Protocol/Infrastructure for communicating between applications over a network

I have a C++ appli开发者_高级运维cation that currently uses a simple TCP/IP client/server model to communicate between 2 instances of itself. This works fine on a local network, but I would like this to be used across an external network. Currently, maybe due to firewall issues, it is not able to connect across an external network.

I am not an expert on networking, but I was thinking about having a dedicated server in the middle acting as a hub for communications. Will this mitigate firewall issues?

How do networked games communicate with each other? Is there usually a server in the middle or is it peer-to-peer?

In any case, I'd appreciate any advice on protocols and infrastructure to implement a network enabled application.

Regards

I think the problem is dedicated to the NAT as mentioned by cnicutar.

Maybe you want to have a look at libupnp for automatic port forwarding in the hardware firewalls (your router at home)

There is no de facto architecture for multiplayer network games. Both client-server (most MMOs, most PC FPS's and RTS's) and Peer-to-Peer (most console games) are valid approaches.

Juoni Smed's survey in his book "Algorithms and Networking for Computer Games" is a pretty good overview of the different architectures in the wild.

For the specific issues you're talking about, your need for a proxy server, as others have noted, is probably down to NAT issues - the two machines you're trying to get talking do not have public IP addresses. If you want to pursue a Peer-to-Peer architecture (or to have one of your clients act as the server, as many modern Client-Server games do) you will need your clients to talk directly to each other. This can be achieved with NAT Traversal, unfortunately this is a fiddly process.

Luckily you can use a modern framework like the excellent Raknet which includes State Synchronisation, Remote Procedure Calls AND NAT Traversal out of the box. It's free for hobbyist use and is incorporated in to several modern industrial-grade game engines.

The bane of modern internet communications is NAT. Due to NAT (which shouldn't be confused with a simple firewall) a large portion of hosts on the internet don't have a public address and thus can't (easily) accept incoming connections. NAT breaks the internet so badly that people are moving to a totally different scheme, with slightly different semantics, just to get rid of it.

There are basically two class of solutions

• NAT traversal which is sometimes used for peer-to-peer communication. Usually NAT traversal schemes require some publicly accessible server for brokering the initial connection, but the actual communication is done peer-to-peer

• Client-server communication. This is easier (since the server generally should have a publicly accessible address) but also kind of inefficient. For instance, say you've got a peer on the same 10Gb LAN. If you want to send him a file through the server (which happens to be in another country) it's going to take ages instead of seconds.

I'm not sure which one is "generally used". But think of it this way:

• If there is the logical need for a "controller" (say 8 people are playing a strategy game) then you probably need a server
• If any two peers can logically interact without a "controller", you probably want peer-to-peer communication
• If you need to transfer LOTS of data fast (file transfer), you almost surely want p2p.

The easiest way to accomplish what you want is by using sockets(in case you are doing it differently). The way you are connecting your app is usually how it's done. Also if it work sin a local network and it does not over the Internet it must be a firewall issue so try opening ports in your router configuration.

You will have to give more info about your program in order to explain if you should go with peer-to-peer or with a server.