I would like to know useful resources / books which will help in learning about Web Servers, App Servers and basics of web architecture as a beginner.
I am trying to learn how different servers interact with each other. How the browser sends requests to the server and server sends a response. I am interested in learning the inside flows of this process.
You will need to learn about services including (but not limited to) TCP/IP, DNS and HTTP. You will also need at least a basic understanding of routers, switches, cables and the like.
Mike Meyer's CompTIA Network+ study guide will tell most of what you need to know to hit the ground running. The guide comes with a timeline of technologies and protocols, down to cable standards. It eventually hits TCP/IP.
Also check out Wiley's Networking Self-Teaching Guide. It focuses less on hardware near the beginning of the book to leave more room for the concept of networking itself.
If you want to back away from books for a bit when it comes to web servers... Well, just work with this Google search for working with an Apache (HTTP server) installation.
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I have a very general question on how to implement VoIP for our current mobile & Web App. (we have an Android+iOS App and a Web Application based on AngularJS/NodeJS).
What we want to achieve
In the first step we want to achieve inter Application Voice and Video Calls. Later on we might expand into outbound calls into the normal telephone network. But this post is mainly for getting info on how to implement only our first step.
general thoughts
We had some experiences with Asterisk before which turned out to be far from easy. So for this project we wanted to get some feedback before actually implementing anything.
thoughts on technology
At first I thought it might be a good idea to use WebRTC, but since it's only supported on Chrome, FF and Opera for the moment and pretty much is unsupported for native mobile Apps we think that WebRTC is probably out of the picture for now. (or do you think otherwise?)
After searching the web a bit more we found this: http://www.webrtc.org/native-code
Has anyone experience with this libs? It seems to us, that this could be the best solution for a modern voip solution (and also would allow us to skip the asterisk server)
The second idea would be to setup an Asterisk Server for ourselves. Every time a user logs into the App we would connect him as a SIP Client to the asterisk. If one user calls the other one we think we should be able to make the call for example with the node package Asterisk Manager API (https://github.com/pipobscure/NodeJS-AsteriskManager).
The third idea would be to use a SIP Provider, but at the moment I'm not sure if that's really the best idea.
Since we're no VoIP experts, are there any other possibilities for VoIP integration into our apps?
Any thoughts on that subject would be very appreciated! Thank you!
The main factor is the network configuration that you app will be working with. Given you're using mobile clients and web apps it's almost certain that you're using the internet and also likely that you'll have 3G and 4G mobile networks in the mix (3G/4G cause a lot more problems for VoIP than WiFi).
Given the above assumption holds the biggest challenge your app will have is establishing media (audio and/or video) connections between mobile clients which are behind different NATs and in a lot of cases multiple NATs. There is almost no chance you'd be able to get by without a server here. The server will be needed to act as a relay point for the media streams for the mobile clients. You will use the RTP protocol for the media and working out how to get it reliably from client A to client B is your biggest obstacle. The signalling side - whether it be SIP, web sockets or something else - will be secondary (note both SIP and WebRTC use RTP to carry the media).
If I were in your shoes the steps I'd take would be:
Install and try out some softphones (blink, bria, zoiper et al) on your own mobile devices, find a SIP provider that supports video calls and get some experience with calls. It may not be the experience you anticipated...
Once you are comfortable with the softphone experience you would then need to make two decisions:
Whether to deploy your own server or use an existing provider,
Whether to write your own client, find an existing one or something in between.
I can answer the deploy your own server question. You don't want to do that unless the VoIP part of your app is going to be something you charge for and make a good margin off. Running a VoIP server and all the security and network considerations that go along with it is a full time job. It may start out being easy but once a few customers start connecting and the fraudsters come along it will take on a life of its own. In the decade I've been messing around with SIP I'd estimate 75% of providers have gone out of business and it was their full time job.
Besides all that I'd be surprised if there wasn't a SIP provider that suited your needs. These days there are highly sophisticated services available that led you control every aspect of your call flow with your own code (anveo, tropo, twilio) right down to free services (sip2sip, sipbroker) that may be all you need to get started.
For the client software there are various SIP SDK's you'll be able to leverage (pjsip).
i'm starting to develop a web application for which I need real-time capability. In particular, as result of a server-side event (without client request), the client must refresh the view. The best solution seems to be a websocket communication.
My doubt is mainly between Node.js and JavaEE 7. Which language do you recommend for development? And with which framework?
The main requirements are:
Interoperability with browsers
Support for mobile devices
Availability of tools for the creation of the graphical interface
Thanks
The question is a bit broad and leads to opinion-based results - that's why it is likely to get close votes, so don't be surprised if it happens ;-)
Nevertheless, I would generally state, that "web application" and "real time" won't work together, because you have components like the network or containers in between which you don't control and thus cannot guarantee real-time requirements.
But I assume, that you are more looking for an "instant" reaction, so that your clients get informed instead of having to ask for something. In that case, web sockets are the state of the art for doing so.
Regarding technology selection, I don't think one is better than the other, it is more a question about available skills or your general programming model or customer requirements. I would think you can perfectly use Java EE 7 for that.
As a reference on that topic, I visited Adam Bien's workshops last year and he talked about an example, where he had a huge number of clients which communicated with a Java EE app server using web sockets.
I was trying to make a simple multiplayer (P2P) board game that connects players over the internet. So far, the only networking applications I've worked on only communicate with permanent web servers via HTTP.
After some preliminary reading, I learnt that most devices are subject to NAT nowadays, which makes P2P connections a pain to establish. I've read about 2 ways around the NAT hurdle:
Set up a central server to facilitate NAT punch-through.
Use Internet Gateway Device (from UPnP) to do automatic port-forwarding.
I haven't delved into the details yet, but it seems like NAT punch-through requires me to set up a permanent matchmaking server (for which I doubt is within my budget) and to administer it (which I have no experience in). UPnP seems like the way to go.
Would you say that my assessment is accurate? Are there any other options? Is there anything else I should take into account before designing/implementing my game?
(I'm planning to write my game using Qt, to support multiple platforms. Someone has made a Qt-based P2P file sharer using the MiniUPnPc library, so I'm thinking of studying that implementation)
One thing you can do to avoid the issue all together is just require your end user to make a local version of the app server and forward the ports themselves. Just give them an option to either "Create Game" or "Join Game", and if they create a game make them specify the port they want to run it on. Then it's their responsibility to make sure that port is open.
Having said that, I recently went through setting up a matchmaking style networked game using Unity3d and I can comment on setting up a matchmaking server within that framework.
There are 2 pieces to the process, the MasterServer and the Facilitator, where the MasterServer just holds all the game related information and the Facilitator handles incoming connections to the server.
Because the MasterServer/Facilitator are only handling connection information, they're fairly light processes and you can just run them in the background on your home machine if you don't mind leaving your machine on all the time.
It pretty much regulates itself once you have it up and running. It's not any more difficult than running a standard web server anyway.
I haven't explored using Internet Gateway Device to handle networking, but looking at the wiki for it (http://en.wikipedia.org/wiki/Internet_Gateway_Device_Protocol), it looks like it's just a magic thing to handle NAT punch through automatically. I have done little to no research on this method, but it looks like it might be something that has to be installed on the client end, which I feel like isn't what you want. If you find a way to make it work the way you want, let me know; I'd be curious to see it in action.
I am looking to create a simple mobile agent system which will deal with 4 tasks, i.e 4 different mobile agents jobs: Database update, meeting scheduling, network services discovery and kernel update.
I have done my research and have seen different frameworks such as Aglet, Jade, agent builder etc. My question is which one should i use? Also i need to setup the base code for it to work, can someone point me to a site or help me to setup the basic functions of the mobile agent?
I've read about tahiti server for the Aglet model. I'm quite confused about how to set up the mobile agent system. Any help would be much appreciated.
I have also tried to it using RMI. I had created a method of type agent, but i couldn't pass it through remote method implementation. I was reading about tcp and udp socket programming. I was thinking may be it would be more fair to do it using socket programming. In this case, would this be called an agent? I was thinking about the server sending datagram packets to multiple clients.
You need to ask yourself why you want to use mobile agents at all. The notion of a mobile agent was popular in the agent research community in the early 90's, but fell out of favour because (i) it wasn't clear what problem it was solving, (ii) the capability to allow arbitrary code to migrate to a particular computer and execute with enough privileges to access local data and services is very open to abuse, and (iii) all of the claimed benefits of mobile agents can actually be achieved though web services (REST or otherwise) and open data formats such as RDF. Consequently, few, if any, mobile agent platforms have been properly maintained since the early experiments.
It also sounds as though you need to be clear which end-user problem you want to solve. Scheduling a meeting and updating my kernel are very different tasks - I'd be very uncomfortable with a program that claims do both. If your interest is in the automation of system maintenance tasks, such as DB tuning and kernel patching, on large networks you might want to look at the SmartFrog project, or read up on autonomic computing.
I use JADE and I agree with the first guy, agent systems usually take alot of overhead to going so if you can avoid it, please do. If however you choose to proceed choose a platform with alot of support and a big user group.
Jade has some neat features like a directory facilitator DF, which works like a yellow pages so other agents don't have to know what agents are running and what services are supplied they can simply inquire by the DF.
Also JADE ContractNetBehaviours help simplify communication.
I'm developing a chat application (in VB.Net). It will be a "secure" chat program. All traffic will be encrypted (I also need to find the best approach for this, but that's not the question for now).
Currently the program works. I have a server application and a client application. However I want to setup the application so that it doesn't need a central server for it to work.
What approach can I take to decentralize the network?
I think I need to develop the clients in a way so that they do also act as a server.
How would the clients know what server it needs to connect with / what happens if a server is down? How would the clients / servers now what other nodes there are in the network without having a central server?
At best I don't want the clients to know what the IP addresses are of the different nodes, however I don't think this would be possible without having a central server.
As stated the application will be written in VB.Net, but I think the language doesn't really matter at this point.
Just want to know the different approaches I can follow.
Look for example at the paper of the Kademlia protocol (you can find it here). If you just want a quick overview, look at the Wikipedia page http://en.wikipedia.org/wiki/Kademlia. The Kademlia protocol defines a way of node lookups in a network in a decentral way. It has been successfully applied in the eMule software - so it is tested to really work.
It should cause no serious problems to apply it to your chat software.
You need some known IP address for clients to initially get into a network. Once a client is part of a network, things can be more decentralized, but that first step needs something.
There are basically only two options - either the user provides one (for an existing node of the network - essentially how BitTorrent trackers work), or you hard-code in a gateway node (which is effectively a central server).
Maybe you can see uChat program. It's a program from uTorrent creator with chat without server in mind.
The idea is connect to a swarm from a magnetlink and use it to send an receive messages. This is as Amber answer, you need an access point, may it be a server, a know swarm, manual ip, etc.
Here is uChat presentation: http://blog.bittorrent.com/2011/06/30/uchat-we-just-need-each-other/