I'm working on an application that does VoIP, Cam-streaming and file transfers at the same time. Currently it runs under Windows, OS X, Android and iPhone/iPad. As you may understand, this can create quite some network traffic, especially if several people on the same LAN does it simultaneously. As a result, VoIP quality suffers.
I figure that the best theoretical solution is to ask the local wi-fi router politely if it can prioritize the VoIP traffic. Unfortunately, most of the traffic streams, including SIP for VoIP and Video is encrypted and sent over TCP. So the router has no way to figure out what TCP/UDP streams does what.
I have looked briefly at UPnP QoS. From the specifications, it's just what I need. But I don't know if it is widely available for today's home routers. I also don't know if it actually works the way I want. To put it simple: For VoIP, I want to specify a stream by it's endpoints, and tell the wi-fi router/home network to give it minimum latency.
So my questions are really:
Is it worth the effort to dig further into UPnP QoS?
Is this widely adapted by modern home LAN hardware (wi-fi routers)?
Are there better approaches to consider?
I also noted that Samsung has a patent pending for this, and I am concerned about the implications.
I have not found any really nice API's for UPnP and QoS, but I guess it's possible to cook something together with curl or boost::asio. If I do, is there any interest for a C++ Open Source library for this purpose?
Encryption doesn't play a part in QoS as encryption is (usually) at the application level not the TCP/IP level.
More likely your problems are related to http://www.bufferbloat.net/
Related
I am wondering if it is possible to limit/control ethernet upload and download speeds on specific transport layers (tcp/udp) using c++? I am trying to make a simple to use program that can control the speeds of any device that the ethernet is connected to. For example: Computer B is connected to computer A via Internet Connection Sharing, I use my program to limit computer B's download or upload speed to 120kbs (or any number i choose), with this I would also like to choose udp or tcp.
Basically, I want to create my own program similar to net limiter and other such software, but I also want to add my own features which many of which lack for my needs. These other features are easy enough, but I have no idea how to go about the actual limting process.
The way forward in the general case you ask about would be to create a virtual network adapter and all the monitored route traffic through it. Once that was done, then you can monitor streams between hosts or on specific ports.
Not an easy job... A starting point would be the Windows device driver kit.
If you were prepared to limit just one app, and could modify it, the task would be much simpler... wget and curl for example both offer limiting.
HTH, Ruth
Let's say I have a server, and two clients connected to it. (via TCP, but it doesn't matter)
My goal is to allow a direct connection between those two clients. This is to allow direct voice contact between two players, for example, or any other client plugin they may have installed which don't need server interaction (like playing some kind of random game between the two). The server can be there to help setting up the connection.
From duskwuff's answer, I got several leads:
http://en.wikipedia.org/wiki/STUN which describes an algorithm to do that, and
http://en.wikipedia.org/wiki/UDP_hole_punching
From those, I got more leads:
http://www.h-online.com/security/features/How-Skype-Co-get-round-firewalls-747197.html
http://nutss.gforge.cis.cornell.edu/stunt.php -- A possible STUN implementation with TCP
With time, I could surely work out something for my program. For now I'm using C++ and TCP (Qt Sockets or Boost sockets), but if needed I don't mind doing UDP in C and wrapping it.
The bounty is there for any programmer having experience with those in C and C++ that may give tips to make this easier, by linking to example programs, updated libraries, or any other useful information. A documented, flexible & working C++ TCP implementation would be the best but I'll take what I get!
Punching TCP holes in NAT is sometimes/often possible (it depends of the NAT behavior). This is not a simple subject to learn, but read the corresponding chapter about NAT traversal from Practical JXTA II (available online on Scribd) to understand the nature of the issues to solve.
Then, read this. It comes from the guy who wrote that: http://nutss.gforge.cis.cornell.edu/stunt.php (one of the links in your question).
I am not a C/C++ specialist, but the issues to solve are not language specific. As long as you have access to TCP from your code base, that's enough. Keep in mind that implementing UDP traversal is easier than TCP.
Hope these tips help.
P.S.: I am not aware of a C/C++ implementation of the solution. The code mentioned in Cornell's link is NOT operational as confirmed by the author. I tried to resuscitate it myself, but he let me know it was completely tweaked for research purposes and far from production ready.
I'm not aware of any way to reliably punch through firewalls for TCP, but there's a similar method for UDP traffic that's pretty well documented:
http://en.wikipedia.org/wiki/STUN
http://en.wikipedia.org/wiki/UDP_hole_punching
A few links to projects that might be of interest or helpful:
http://sourceforge.net/projects/stun/
http://udt.sourceforge.net/
http://www.telehash.org/
You're looking for rendezvous server for NAT hole punching: the server that is publicly accessible (not behind NAT/firewall or they are properly configured) to help computers behind NAT/firewall to establish peer-to-peer connection.
UDP is more popular in NAT punching because provides much better results than TCP. Clear and informative description of UDP NAT hole punching can be found here.
If you need reliable communication, you can use reliable protocols over UDP:
SCTP (libraries) - standardized one, or
one of many custom protocols, e.g. RakNet (I used this library, it's quite mature and feature-rich and has NAT punching implementation), Enet or many others (Q8)
Ephemeral ports won't magically eliminate the need to relay through the server, because they are only valid during the life of the session opened through a well known service port. Basically ephemeral ports depend on a server session.
You will need to use the server to relay communications between both clients, that is act as a proxy server. One option would be to setup a SSH tunnel through a SSH proxy server, with the added benefit of security.
Still this doesn't guarantee that the firewall won't block the connection. That depends on the firewall type and configuration. Most residential routers that act as firewalls, by default block all incoming connections. This is normally fine because most of the time the computers behind the firewall act only as clients, which initiate the connections to the outside. And this setup varies, because some restrict initiating connections only to well known service ports like HTTP, HTTPS, FTP, SFTP, SSH, etc., and if your proxy server uses a non-well-known-service port then the connection will be blocked.
But firewalls can be setup to block outgoing traffic also, this is most common in corporate networks, which don't even allow direct connections to web servers and route everything through proxy servers, in order to control resource usage.
You can also research on the use of UPnP to open ports dynamically.
I have a certain application running on my computer. The same application can run on many computers on a LAN or different places in the world. I want to communicate between them. So I basically want a p2p system. But I will always know which computers(specific IP address) will be peers. I just want peers to have join and leave functionality. The single most important aim will be communication speed and time required. I assume simple UDP multicast (if anything like that exists) between peers will be fastest possible solution. I dont want to retransmit messages even if lost. Should I use an existing p2p library e.g. libjingle,etc. or just create some basic framework from scratch as my needs are pretty basic?
I think you're missing the point of UDP. It's not saving any time in a sense that a message gets faster to the destination, it's just you're posting the message and don't care if it arrives safely to the other side. On WAN - it will probably not arrive on the other side. UDP accross networks is problematic, as it can be thrown out by any router on the way which is tight on bandwidth - there's no guarantee of delivery for it.
I wouldn't suggest using UDP out of the topology under your control.
As to P2P vs directed sockets - the question is what it is that you need to move around. Do you need bi/multidirectional communication between all the peers, or you're talking to a single server from all the nodes?
You mentioned multicast - that would mean that you have some centralized source of data that transmits information and all the rest listen - in this case there's no benefit for P2P, and multicast, as a UDP protocol, may not work well accross multiple networks. But you can use TCP connections to each of the nodes, and "multicast" on your own, and not through IGMP. You can (and should) use threading and non-blocking sockets if you're concerned about sending blocking you, and of course you can use the QoS settings to "ask" routers to rush your sockets through.
You can use zeromq for support all network communication:
zeromq is a simple library encapsulate TCP and UDP for high level communication.
For P2P you can use the different mode of 0mq :
mode PGM/EPGM for discover member of P2P on your LAN (it use multicast)
mode REQ/REP for ask a question to one member
mode PULL/PUSH for duplicate one resource on the net
mode Publish/subscribe for transmission a file to all requester
Warning, zeromq is hard to install on windows...
And for HMI, use green-shoes ?
i think you should succeed using multicast,
unfortunately i do not know any library,
but still in case you have to do it from scratch
take a look at this:
http://www.tldp.org/HOWTO/Multicast-HOWTO.html
good luck :-)
I have a C++ application 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.
For a while, I've been interested in creating a proof-of-concept chat program using C++. I have given the idea a lot of thought and even wrote down the beginnings of how I would design the system, but I have hit a barrier in my thinking when it comes to the implementation.
I want to know what an implementation of a peer-to-peer chat client with a server to route connections would look like in C++.
The server would be used as a central registry of the peers, but not used as the primary connection. The server would not interact with the clients in any way except to assign connections between peers to achieve an optimal path between peers. In a first version, it would merely be a directory to which all clients connect, and the clients can then use the directory to connect to the other clients available for chat. (I hope that explains it a bit more). :)
You should look at the XMPP stuff. It is all about routing and co-ordinating messaging. It uses de-centralization and a peer-to-peer like architecture.
There are also plenty of open source implementations. For example,
Jabber.org
I cannot really think at something better than the chat example in
the Boost.Asio documentation. Search for the examples documentation in Boost.Asio.