Lets say I have a server for broadcasting a character's position in an online game and a server for voice chatting with a group of players in the same game. Would the client be able to send data to both servers? Would they connect? Would this work? Would it be practical?
Short answer: yes.
Long answer: That's actually pretty common. Your browser does it all the time, connecting to different servers using different protocols (HTTP and HTTPS, at least), for example. Most mail clients support an even wider range of protocols (POP3, IMAP, SMTP, sometimes NNTP and encrypted variants thereof) and can easily handle multiple servers in parallel. A networked game client works, on the network protocol level, exactly like those, so there's nothing out-of-ordinary nor impractical in doing so.
Related
I'm looking for the name of a protocol and example code that permits handing off IP/port connections to establish unmediated P2P after introduction through a server.
Simple example:
You and I both start chat programs that connect to chatintroduce.com (fictional server). I send you a "Hi! Wanna chat?" message. It doesn't get sent. Instead my chat program tells chatintroduce to send your chat program a request for connection. You respond to a prompt and your chat program tells chatintroduce to broker the connection. Chatintroduce establishes an initial two-way connection between us. Now, this final step is important, chatintroduce releases control and our two chat programs now talk directly to each other without any traffic through chatintroduce.
In other words, I construct packets which have your IP address and you receive them without interference from firewalls, NATs or any other technologies. In other words, true peer-to-peer connection independent of intermediate server.
I need to know what search terms to use to find appropriate technology. An RFC name would suffice. I've been searching for days without success.
I think what you are looking for is TCP/UDP hole punching which typically coordinates the P2P connection using a STUN server to determine the "capabilities" of the firewalls (e.g. is it a full cone nat? symmetric?).
https://en.wikipedia.org/wiki/Hole_punching_(networking)
We employed this at a company I worked for to create a kind of BitTorrent that could circumvent firewalls for streaming video between two peers.
Note that sometimes it is NOT possible to establish a connection without the intermediary.
What you are looking for is ICE protocol. RFC 5245. This protocol is used for connecting two peers through NAT traversal. There are some open source libraries and also some proprietary libraries for this. You can search google with ICE implementation.
You will also need to read about some additional protocols. These are used with ICE protocol. They are STUN and TURN.
For some cases you can't make P2P call 100% time. You will have to use a relay server. Like if the NAT combination of two peers are Symmetric vs Symmetric/PRC. That relay server is called TURN server.
Some technique like Port forwarding and TCP/UDP hole punching will help you to increase P2P rates.
See this answer for more information about which combination of NAT will require a relay server and which don't.
Thank you. I will be looking further into ICE, STUN, TURN, and hole-punching.
I also found n2n which looks like almost exactly what I wanted.
https://github.com/meyerd/n2n
http://xmodulo.com/configure-peer-to-peer-vpn-linux.html
With n2n, one makes a VPN with a super node that all other edge nodes know.
But once the introductions are made, the super node can be absent.
This was exactly what I wanted. I hope it works across platforms (linux, MacOS, Windows).
Again, I am still researching before implementation, so your advice was very important to me.
Thank you.
Use PJNATH. Its open source.
http://www.pjsip.org/pjnath/docs/html/
There is not much open source on NAT Traversal. As far as I know PJNATH is good.
For server you can use Google's Open source STUN and TURN server.
I want to setup a personal videoconferencing service for my family, friends and myself. The main problem I have with current options is that they are either closed-source and centralized (GG hangouts, skype) or open-source but not working in corporate environment or in hotels (due to strict firewalling rules and the "Skype is going through, if you want VOIP use that" kind of netadmin reaction).
I have two solutions then. Either setup a STUN/TURN relay server and use XMPP and SIP as I used to, but that would require my friends to setup that too. Or setup a whole VOIP server. 2 solutions come to mind: SIP and XMPP. Though to my knowledge, each of them ultimately uses the (S)RTP/RTCP protocol.
And that's the problem. Out of the specific signaling part used by the two of them, I really can't figure out the difference between them, their typical use case.
I think you're right in that as far as setting up a video conferencing system XMPP and SIP are equivalent. They both are signalling only protocols and the media sessions they set up typically use RTP (although they can both be used to set up any kind of session you want but RTP is the norm).
The biggest problem is also going to be the one you mention about getting video streams out of a corporate firewall. Skype overcomes this obstacle by sending it's media over an SSL connection and is thus able to get through firewalls. Theoretically you could do the same with RTP and in the past I once used openvpn connections with a SIP client to test some audio calls. My experience wasn't great as the audio was very choppy, assumedly as a result of all the extra packaging that is required to get the high volume of small audio packets from one end to the other. That was nearly a decade ago though so perhaps with the better CPU and bandwidth resources available now it would work better.
Personally I think I'd stick with Skype as it's going to be a big hassle to set up your own system. If you were to go ahead with your own the first option I would try would be Asterisk combined with openvpn so that if the clients were behind a firewall or had NAT issues they could connect over it.
At the bottom, it's all about socket communications. If there is some way to get the ip of the both users, why can't the connection be directly setup between the users instead of having to go thru a server in the middle?
My 2 cents:
No one out there forces us to have a server based real-time communication model. Infact XMPP have an extension called "Serverless Messaging" which defines how to communicate over local or wide-area networks using the principles of zero-configuration networking for endpoint discovery and the syntax of XML streams and XMPP messaging for real-time communication. This method uses DNS-based Service Discovery and Multicast DNS to discover entities that support the protocol, including their IP addresses and preferred ports.
P2P chat applications have been for over a decade now. Having a server in the middle is purely a decision dependent upon your application needs. If your application can live with chats getting lost while the user was transitioning between online/offline status, then you can very well have a direct P2P model going. Similarly, there are a loads and loads of advantages (contact list management, avatars, entity discovery, presence authorization, offline messages, ....) when it comes to choosing a server based messaging model. If you try to have all this right inside your P2P based clients, they might die or under-perform because of all the work they will need to perform by themselves.
"WebSockets" were not designed for P2P/Serverless communication, rather they were designed to provide a standardized PUSH semantic over stateless HTTP protocol. In short, "WebSockets" is a standardized way replacing hacky comet, long-polling, chunked-encoding, jsonp, iframe-based and various other technique developers have been using to simulate server push over HTTP.
Named WebSockets (if someday it is fully and widely supported) could be the solution.
http://namedwebsockets.github.io/spec/
Named WebSockets are useful in a variety of collaborative local device
and local network scenarios: Discover matching peer services on the
local device and/or the local network.
Direct communication between users is possible in Peer To Peer (P2P) networks. In P2P each participant can act as client as well as server. But for P2P networks you need to write a separate program to make the communication possible.
Web Sockets let you leverage existing common browsers as clients. All depends on what is the purpose of your application and how you want to deploy it.
If there is some way to get the ip of the both users
You nailed the answer right in your question.
Most machines I use have IP address of 192.168.0.10 (or similar from 192.168. private network) and are deep, deep behind several layers of NAT. With the end of free IPv4 address pool and IPv6 nowhere near sight, this is the reality most users live. Having a stable intermediary of known, routable address helps a ton working around this issue.
WebSockets don't allow the socket to listen for connections, only to connect as a client to a server (not reverse). Technically they could make it allow this, but as far as I understand the spec doesn't currently (nor is it expected to) allow listen functionality for WebSockets.
The new WebRTC (http://www.webrtc.org/) spec looks like it might support peer-to-peer connections. I have not played with WebRTC at all so I'm not in a position to comment on it. I think it would be a bit more involved than WebSocket stuff. Maybe someone who knows WebRTC better can chime in. (Also apart from the latest version of Chrome I'm not sure if any of the other browsers really support WebRTC yet).
Does using web sockets actually mean browsers will be able communicate with xmpp servers (any other IM servers) directly ?
Thx.
No. Allowing TCP-level access to arbitrary servers would cause all kinds of security problems. Imagine a website which caused every user to connect to an SMTP server and start sending spam emails… suddenly you have a massively distributed spam attack, especially if combined with an XSS attack on a major site. Web Sockets has a small amount of framing around it designed to make such attacks impossible, without adding too much overhead over TCP.
One day. It's likely that we'll define an XMPP sub-protocol for websockets that can replace BOSH(XEP-0124/0206) when both the client and server support it. In the meantime, BOSH is widely implemented.
you can think of HTTP polling ....
and transfer xmpp data along 8080 port..
I am asking this question as a small part of my question series regarding game programming .
Refer this question as the main one .
Now suppose I want to develop a game on iphone - a simple online multiplayer board game.
Suppose its a casino table.
In the main question ChrisF has tell me of sort of Client - Server architecture for iphone online multiplayer game.
I want to know what sort network programming I have to do for this type of application .
What will be the responsibilities and activities carried out by client and server .
You can provide me link, tutorials or to the point answers , anything will be great help for me and will be really appreciable .
thanks
You'll want to write a socket application running on a server. When you have access to a wifi access point or edge/3g you can send data to it from your iphone application. This server can then handle the incoming data and send an appropriate reply to the people connected.
For server socket programming, take a look at this guide - http://beej.us/guide/bgnet/.
For iphone specific socket programming, take a look at the samples supplied with the Iphone SDK. This link also has some basic information.
A simple online multiplayer board game
Given that the iPhone isn't always connected to the internet, you might need a server to store state. Alternatively you could always stipulate that if one person loses their connection the game finishes.
Client to client would be the obvious choice for the latter. Both clients have a port they listen to, and send the other commands based on the board state. Like almost all online games the obvious choice would be to use UDP as it's fast and compact.
For the server architecture you will of course need some kind of server listening for commands and a game number. It would store your state in a datastore on the server, a mySQL database for example. UDP or even SOAP or JSON over HTTP would be the two obvious choices for this.
This second approach using JSON/SOAP route would be a lot easier for you to get started with, assuming the iPhone has a decent JSON or SOAP library which is not likely. I have no idea about UDP in Objective C, however in C it requires a certain level of knowledge which won't get you something to play with quickly.
As you already said, you will need a server, but you can have two kinds of design:
The server can serve only as a gateway between the players to connect one to each other: it's two uses are, first, to list the running games, and second, to list the IP addresses of the players so that each client will read the IP addresses and connect to them. This will require less bandwidth and processing power for the web server and more for the client which will host the game. In this configuration, one of the clients will act as a server and will send data to the others. If your game has only one of the players playing at a time, and not a huge lot a players, this is what you should use as what you pay is the server's power.
The server can also store all games' states: it might require far more processing power and/or bandwidth depending on your game.
Anyway, most of the time you will want only one machine (which can change during the game as in the first case) to do the processing and the others will only receive the computed data.
To program a networked game, you will need knowledge of sockets (deep knowledge in the first case because you will have to deal with NAT issues, routers blocking the way between clients). The guide to that is Beej's Guide to Network Programming, the number one ressource on this topic, although it doesn't focus on games.
If not too much processing is needed on the WWW server, you could deal with it with server scripting languages like PHP along with MySQL, but you're most likely to use your own server programmed in C++ (or in C). If you use C++, you might want to use an already existing library such as RakNet.
The client will obviously be programmed in Objective-C as it's on the iPhone. I believe there is a good networking framework looking at the number of online games, so you might as well not want to use an external server networking library.
It might be a bit too much for what you want to do, but you could also use the well known Torque Engine.