I am building an app with Socket.io, which allows to keep constant communication between clients and the server. I recently discovered AppSync, but I don't know if the WebSocket connection will die after an hour (AWS limits the WebSocket connection to 1 hr in other services). I checked the documentation for AppSync, but I do not see anything about this. Does it also handle automatic reconnection? Is it possible to detect when a webSocket disconnection has occured?
which platform are you targeting? JS/iOS/Android? There are respective client libraries which will help you interact with AppSync and manage automatic reconnection.
iOS https://github.com/awslabs/aws-mobile-appsync-sdk-ios
Android https://github.com/awslabs/aws-mobile-appsync-sdk-android
JS https://github.com/awslabs/aws-mobile-appsync-sdk-js
General documentation for the AWS frameworks https://aws-amplify.github.io/docs/
If you need further information about them, I'd suggest taking a look at the links above, taking a look at the Issues or opening one with the respective repo's with any questions.
Hope that helps!
Related
I am working on an automation project using Raspberry pi and Windows IoT. Is it possible to broadcast to a web page, similar to Server-Send-Event? I am monitoring certain events and instead of calling server every few seconds for updates, I would like server to send the alert to web page direct. Any help would be greatly appreciated.
I think you can use WebSockets. WebSockets are an advanced technology that makes it possible to open an interactive communication session between the user's browser and a server. You can refer to this sample. Or you can use IoTWeb to embed a simple HTTP and WebSocket server into your application.
Update:
WebSockets are a great addition to the HTTP protocol suite, but there are numerous situations where they cannot be used.
Some companies have firewalls that will prevent WebSockets from
working.
If you are deploying software in a shared hosting
environment, you may not be permitted to use WebSockets.
If you are
behind a reverse proxy that isn’t configured or the software doesn’t
support pass-through of WebSocket protocol, WebSockets won’t work.
Another option is long polling,the browser does an XHR request and the server simply doesn’t respond until it has something to send. But in this way, if you want to do 2-way communications with the server, you are effectively using 2 sockets. One is tied up hanging/waiting for the long poll response, and the other is sent by the client to send new information to the server. Long polling is also problematic because the client has to be able to handle XHR errors, some of which are tricky to handle or even impossible to handle. You can search more differences and disadvantages from internet.
I need to make TCP based decentralised chat app for local network. By decentralised I mean there is no central server. Each entity on a network should have server/client architecture. When app starts it should check which user is online ( already running the app ). My question is how can i check that? Can i do it by trying to connect via connect() function from socket library? I'm new to programming, especially socket programing, so if it's a dumb question sorry in advance.
You should definitely study how other decentralized applications do this. There are lots of techniques.
Each instance of the application should, as part of its server functionality, track the addresses of other instances of the application. Each instance should, as part of its client functionality, keep track of a few instances it can connect to. Prefer instances that have been around for a long time.
The software should include a list of servers that have been running for a long time and are expected to typically be available. You may wish to include a fallback method such DNS, maintained by anyone willing to keep a list of well-known servers offering access through a well-known port. The fallback method can also be IRC or HTTP.
If you want to stay decentralized, you might want to try multicasting or broadcasting a request packet to all hosts on the network to discover other instances of your chat application.
Something similar has been implemented in Pidgin, named Bonjour. It works quite nicely and provides chatting capabilities on a local network. More specifically, it is defined as a Serverless Messaging part of XMPP.
If you are looking for code examples, have a look at one of my projects where I use multicast to discover hosts on the local network that provide a specific service: Headers and implementation.
I am thinking of adopting Loopback.io to create a REST API. I may need the following approach: an inTERnet server (run by me) to which clients connect, plus a fallback inTRAnet server to which clients connect only in case the internet connection is down. This secondary fallback server should then replicate data on the main server when the internet connection is up and running again. As clients are on the same inTRAnet they should be able to switch automatically to the fallback server. Is this possible as an idea and if so, what do you recommend i start digging into?
Thank you all!
Matteo
Simon from my other account. I believe what you want is possible as you can use whatever client side technology you want with LoopBack. As for easy solutions, I'm not familiar enough with Cordova to give any insight there.
It is definitely possible, but I suggest going through the getting started tutorial first. You'd probably create two application servers and have another proxy in front to route the requests to server a or b based a heartbeat from the main server. You would have to code all the logic and set up the infrastructure yourself though.
I have a client company with a simple web application (Python Flask) and I need to add a phone notification functionality to it.
The main requirement is that the app should call users, play a certain sound file and accept some tone input ("Hello! This is an automated message from your WebApp account. You have a meeting with $John today at $5pm. Please press 1 to confirm").
The other requirement is that the solution should be relatively cheap and fast to market.
I have done some research already and it seems that there are a few consequent steps to achieve that:
Set up an Asterisk or a FreeSwitch server;
Set up a SIP account;
Write some business logic for the Asterisk server which allows to make calls and play sounds via a SIP account;
Write an API at the Asterisk server and expose it to the Python Flask web app.
Do I miss something here? Can any of the steps be omitted anyhow? Can I do it simpler?
the fastest way to get it working is to use one of the cloud voice services with speech synthesiser. Here's a short list to check out:
Twilio
Tropo
Plivo
Here I listed some details.
Those services charge you per minute, plus you may have to pay some monthly fee.
If you want to run an independent and standalone service, I would recommend FreeSWITCH instead of Asterisk. It's got reach integration possibilities and API. You will need to read the FreeSWITCH book in order to understand how it works and how to build your service.
I agree with Stanislav Sinyagin on the cloud based solutions, but I would add one more, Voxeo Prophecy. Tropo is from Voxeo, but they have offered Prophecy as a solution for a lot longer and it supports the open standards CCXML and VoiceXML. The advantage of CCXML for outbound notification applications is you have a lot more control of the notification process.
The Prophecy platform has excellent call progress analysis (CPA) which will allow you to determine whether a machine or a human answered and handle the call accordingly. For example, it does not make sense to ask a machine to "...press one to confirm". Instead you may want to leave a message that provides a call back number for the user to confirm with after they have listened to the voice message. The CPA can be used to leave a message on a machine at the correct time (when the greeting message has stopped) so that you do not get clipped messages in the voice mail. CPA will also allow you to provide detailed reports on who was notified and for those that did not it can tell you whether it was a bad number (received a SIT tone), a modem or fax answered, or ring-no-answer (pretty rare these days). These type of details can factor into your retry process for failed notifications.
The other advantage to using Prophecy and open standards is your application will be portable to other IVR systems that are VoiceXML/CCXML compatible if you ever want to migrate. Tropo, Twilio, and Plivo all use proprietary API's which does not allow you to move your applications to other services. Prophecy is also available as a software solution so that if you want to take it out of the cloud you can run it on premise. You can get a two port version for free to try it out.
There is excellent documentation on developing outbound notification systems on Voxeo's developer site. Take a look at the CCXML documentation in section F on Outbound Dialing.
Not sure which development languages you are familiar with, but if you are used to ASP.NET MVC there is an open source project called VoiceModel that makes it easier to develop VoiceXML applications. The other advantage of VoiceModel is that you develop your application once and it will run on any VoiceXML compatible platform and Tropo. They are currently working on adding outbound notification support in this project that will work for both Tropo and VoiceXML.
Third party solutions listed are your easy choice. Running your own asterisk is also suitable for what you want to do, but i think for only this much it would be overkill, from an operational perspective.
In asterisk, you can originate a call that has the 2 variables you need with an (basic-authenticated) HTTP request. You will also need some settings and a tiny dialplan. Setting up the SIP account is easier or more difficult, depending on the documentation from the provider. Most of them have detailed documentation for configuring asterisk (not so much so for freeswitch). Keeping the damn thing alive is what's gonna get to you :)
I've read just about every article available on the Internet regarding "Error #2048" and "Security sandbox violation". I've tried every solution offered, but the problem still persists.
The detailed version of my efforts can be found at the following link:
http://forums.adobe.com/message/4668901#4668901
To summarize, I'm using Flash Professional CS6 with AS3 trying to establish a binary socket connection to a server I developed in C#. I discovered at one point I needed to have a policy server to serve up the requested crossdomain.xml on port 843, but despite following every bread crumb I'm still being haunted by "Error #2048: Security sandbox violation".
I ran across a few references that mentioned placing the SWF on a remote server, so I tried this by firing up a VirtualBox session running Server 2012 RC and had the same results--despite browsing the HTML page from the Guest OS.
I've noticed documentation on Adobe is severely outdated, so I don't know if maybe I just missed the announcement that they're pulling socket support for developing your own server or if this is their way to force you into purchasing their media servers.
Perhaps there is another way to go about this, but what I'm looking to accomplish is being able to communicate with a Flash Application to a back-end Server with real-time data. I'm not looking to stream video or music, just text data packets. The back-end Server would be developed using C#.
Any feedback or suggestions appreciated.
Thanks.
The Solution required 3 changes. The first had to do with how the "AddressFamily" was being identified. The next item was changing the IPAddress for the IPEndPoint from a source of an AddressList to "IPAddress.Any". The last item was somewhat odd, as the Server didn't seem to pick up any new connections until I defined the Listener with MaxConnections.
See my Adobe Forum message for more details.