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.
Related
I'm building an app which upon login will connect you to certain ip addresses of which will also be running the same app.
The method of which i believe i should be using is direct tunnelling but as i say im a little new to c++, i have general coding skills, and i have sifted through a lot of forums and sites yet im still very unclear on what the best way forward is to achieve the requirement.
The reason for the connection will be to enable a secure chat, file transfer, and update software auto when connected to the program admin.
All those that have the app installed will once authorised, will be connected to admin client, then from that client all available ip's to connect to will become available to slave clients, this will increase the network size avilable to all users.
so the app needs to be able to handle ports but not via a server, instead it would be direct.
The connections also must ideally be encrypted.
Im kind of looking for what the application RetroShare does, but in text app.
(This is using C++ within Dev C++)
so just to recap, What method should i use to achieve the above?
I would take a look at SDL net to start with, its really simple to learn if you have never done any socket programming before.
for a secure connection you will probably want to start with TCP and then once you get the hang of network programming, start looking at other protocols.
Hope this helped! and good luck.
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'm writing a tcp server for an online turn-based game. I've already written a prototype using php sockets, but would like to move to C++. I've been looking at the popular network libraries (ASIO, ACE, POCO, LibEvent), but currently unclear which one would best suit my needs:
1) Connections are persistent (on the order of minutes), and the server must be able to handle 100+ simultaneous connections.
2) Connections must be able to maintain state information (user login info). [my php prototype currently requires each client request to contain the login info]
3) Optionally and preferably multi-threaded, but a single process. Prefer not to have 1 thread per connection, but a fixed number of threads working on all open connections.
I'm leaning towards POCO's TCPServer or Reactor frameworks, but not exactly sure if they meet my requirements. I think the Reactor is single threaded, and the TCPServer enforces 1:1 threading/connection. Am I correct?
In either case case, I'm not exactly sure how to do the most important task of associating login info to a specific connection with connections coming and going at random.
Boost.Asio should meet your requirements. The reactor queue can be serviced by multiple threads. Using asynchronous methods will enable your design of a fixed number of threads servicing all connections.
The tutorials and examples are probably the best place to start if you are unfamiliar with the library.
You might also take a look at MUSCLE, a multi-user networking library and server I wrote with this sort of application in mind. It's BSD-licensed, handles hundreds of users, and includes a server-side database mechanism for storing and sharing any information you want the clients to know about each other. The server is single-threaded by default, but I haven't found that to be a problem in practice (and it's possible to extend the server to be multithreaded if that turns out to be necessary).
I'm working on a project of which a large part is server side software. I started programming in C++ using the sockets library. But, one of my partners suggested that we use a standard server like IIS, Apache or nginx.
Which one is better to do, in the long run? When I program it in C++, I have direct access to the raw requests where as in the case of using standard servers I need to use a scripting language to handle the requests. In any case, which one is the better option and why?
Also, when it comes to security for things like DDOS attacks etc., do the standard servers already have protection? If I would want to implement it in my socket server, what is the best way?
"Server side software" could mean lots of different things, for example this could be a trivial app which "echoes" everything back on a specific port, to a telnet/ftp server to a webserver running lots of "services".
So where in this gamut of possibilities does your particular application lie? Without further information, it's difficult to make any suggestions, but let's see..
Web Services, i.e. your "server side" requirement is to handle individual requests and respond having done some set of business logic. Typically communication is via SOAP/XML, and this is ideal if you bave web based clients (though nothing prevents your from accessing these services via standalone clients). Typially you host these on web servers as you mentioned, and often they are easiest written in Java (I've yet to come across one that needed to be written in C++!)
Simple web site - slightly different to the above, respods to HTML get/post requests and serves up static or dymanic content (I'm guessing this is not what you're after!)
Standalone server which responds to something specific, here you'd have to implement your own "messaging"/protocols etc. and the server will carry out a specific function on incoming request and potentially send responses back. Key thing here is that the server does something specific, and is not a generic container (at which point 1 makes more sense!)
So where does your application lie? If 1/2 use Java or some scripting language (such as Perl/ASP/JSP etc.) If 3, you can certainly use C++, and if you do, use a suitable abstraction, such as boost::asio and Google Protocol buffers, save yourself a lot of headache...
With regards to security, ofcourse bugs and security holes are found all the time, however the good thing with some of these OS projects is that the community will tackle and fix them. Let's just say, you'll be safer using them than your own custom handrolled imlpementation, the likelyhood that you'll be able to address all the issues that they would have encountered in the years they've been around is very small (no disrespect to your abilities!)
EDIT: now that there's a little more info, here is one possible approach (this is what I've done in the past, and I've jused Java most of the way..)
The client facing server should be something reliable, esp. if it's over the internet, here I would use a proven product, something like Apache is good or IIS (depends on which technologies you have available). IMHO, I would go for jBoss AS - really powerful and easily customisable piece of kit, and integrates really nicely with lots of different things (all Java ofcourse!) You could then have a simple bit of Java which can then delegate to your actual Server processes that do the work..
For the Server procesess you can use C++ if that's what you are comfortable with
There is one key bit which I left out, and this is how 1 & 2 talk to each other. This is where you should look at an open source messaging product (even more higher level than asio or protocol buffers), and here I would look at something like Zero MQ, or Red Hat Messaging (both are MQ messaging protocols), the great advantage of this type of "messaging bus" is that there is no tight coupling between your servers, with your own handrolled implementation, you'll be doing lots of boilerplate to get the interaction to work just right, with something like MQ, you'll have multiplatform communication without having to get into the details... You wil save yourself a lot of time and bother if you elect to use something like that.. (btw. there are other messaging products out there, and some are easier to use - such as Tibco RV or EMS etc, however they are commercial products and licenses will cost a lot of money!)
With a messaging solution your servers become trivial as they simply handle incoming messagins and send messages back out again, and you can focus on the business logic...
my two pennies... :)
If you opt for 1st solution in Nim's list (web services) I would suggest you to have a look at WSO's web services framework for C++ , Axis CPP and Axis2/C web services framework (if you are not restricted to C++). Web Services might be the best solution for your requirement as you can quickly build them and use either as processing or proxy modules on the server side of your system.
I would like to create a connection between two applications. Should I be using Client-Server or is there another way of efficiently communicating between one another? Is there any premade C++ networking client server libraries which are easy to use/reuse and implement?
Application #1 <---> (Client) <---> (Server) <---> Application #2
Thanks!
Client / server is a generic architecture pattern (much like factory, delegation, inheritance, bridge are design patterns). What you probably want is a library to eliminate the tedium of packing and unpacking your data in a format that can be sent over the wire. I strongly recommend you take a look at the protocol buffers library, which is used extensively at Google and released as open source. It will automatically encode / decode data, and it makes it possible for programs written in different languages to send and receive messages of the same type with all the dirty work done for you automatically. Protobuf only deals with encoding, not actually sending and receiving. For that, you can use primitive sockets (strongly recommend against that) or the Boost.Asio asynchronous I/O library.
I should add that you seem to be confused about the meaning of client and server, since in your diagram you have the application talking to a client which talks to a server which talks to another application. This is wrong. Your application is the client (or the server). Client / server is simply a role that your application takes on during the communication. An application is considered to be a client when it initiates a connection or a request, while an application is considered to be a server when it waits for and processes incoming requests. Client / server are simply terms to describe application behavior.
If you know the applications will be running on the same machine, you can use sockets, message queues, pipes, or shared memory. Which option you choose depends on a lot of factors.
There is a ton of example code for any of these strategies as well as libraries that will abstract away a lot of the details.
If they are running on different machines, you will want to communicate through sockets.
There's a tutorial here, with decent code samples.