This is a follow-up to another question I asked, but with more precise information.
I have two fundamentally identical web pages that demo WebRTC, one using XSockets as the backend signaling layer, and one using SignalR as the backend signaling layer.
The two backends are fundamentally identical, differing only at the points where they (obviously) have different ways of sending data down to the client. Similarly, the TypeScript/JavaScript WebRTC code on the two clients is completely identical, as I've abstracted out the signaling layer.
The problem is that the XSockets site works consistently, while the SignalR site fails (mostly consistently, though not completely). Usually it fails while calling peerConnection.setLocalDescription(), but it can also fail silently; or it can (sometimes) even work.
You can see the two different pages in operation here:
XSockets site: http://xsockets.demo.alanta.com/
SignalR site: http://signalr.demo.alanta.com/
The source code for both is at https://bitbucket.org/smithkl42/xsockets.webrtc, with the XSockets version on the xsockets branch, and the SignalR version on the signalr branch.
So my question is: does anybody know of any reason why using one signal layer instead of another would make any difference to WebRTC? For instance, does one or the other send back Unicode strings instead of ANSI? Or have I misdiagnosed the problem, and the real difference is elsewhere?
Figured it out. Turns out that SignalR 1.0 RC1 has a bug in it that changes any "+" in a string into a space. So lines in the SDP that looked like this:
a=ice-pwd:qZFVvgfnSso1b8UV1SUDd2+z
Were getting changed into this:
a=ice-pwd:qZFVvgfnSso1b8UV1SUDd2 z
But because not every SDP had a "+" in it on a critical line, sometimes it would work. Everything explained.
The bug has been reported to the good folks working on SignalR (see https://github.com/SignalR/SignalR/issues/1194), and in the meantime, a simple encodeURIComponent() and decodeURIComponent() around the strings in question fixed it.
Related
We are trying to document our SignalR Hubs via AsyncAPI.
This is the best example so far we were able to find about SignalR and AsyncAPI:
https://github.com/neuroglia-io/AsyncApi/issues/3
When we apply this scenario to our code in a similar manner, we can create a specification, but this specification results in "Empty or invalid document" in asyncapi studio. I cannot understand why.
Another question is, AsyncApi seems to support SignalR because WebSockets is what SignalR uses, but not necessarily. (In our case, SignalR might fall back to Server Events / Long Polling depending on firewall configuration.) Does that mean that the AsycnApi UI will be useless for us when that happens? Or am I mixing things here?
I want to expose multiple BLE services from one device using Qt (on linux), but don't know how to do it if it's even possible.
In my specific case I want my device to be both a heart rate service (HRS) and a cycling power service (CPS).
My testing code is very similar to the heart rate server example from Qt's documentation, http://doc.qt.io/qt-5/qtbluetooth-heartrate-server-main-cpp.html, and I've tried the following two approaches:
Using two QLowEnergyControllers from one application
Using one QLowEnergyController, but adding two different services using bleController->addService().
However it doesn't seems like either one is working properly, or it is just the apps I use for testing that doesn't really handles this properly. I currently use my iPhone 6s with TrainerRoad for testing, and if I just expose one of the services it works well.
Can this be done, and if so, what is the correct way?
I retried this a while back and could successfully provide multiple services using one device. The correct way is to use option 2, so one QLowEnergyController and then add multiple services.
Unfortunately I didn't keep the code from my first attempt, so I can't provide a good answer of what I did wrong. But it works "as expected", no special stuff is needed.
what's the proper way to capture biometric information (pressure, speed...) by signing with a stylus on a canvas developed in a JSP web Page
Alright, since no one else has attempted to answer this question, I shall elaborate on my comment and opefully it will serve as an answer to others as well.
First, Java Server Pages (JSP) is a server-side language. It is meant to run on the web-server and not on the user's browser. The same goes for other server-side languages like PHP and ASP.
So a server-side language is not able to directly interact with devices (keyboard, scanners, cameras, etc). Only when the data is submitted by the browser or client program, the server receives it for processing.
For a device to receive input, there are two key pieces of software needed.
The device driver: which must be installed on the user's machine
The application program to capture inputs and do any processing.
If either one is missing, the device cannot function. And then there's another issues. Depending on the device, there's various feedback from the driver/API that should go back to the application that reads it. For example, if a fingerprint scan was not very successful for some reason, the scanner should tell this to the user. So again, there's the need for interactivity between the device and the user's application.
Thus, using any server-side language is out of the question for such applicatoins.
Now, in order to make this possible, you may use a client-side program. Here are some options.
A native application in VB, C/C++, Pascal or other language. If this is an option, the user must install this application on their computer.
A browser-based program. This can be a program created using JAVA (not Javascript or JSP), or ActiveX component. ActiveX is largely OS/browser dependent. And the TRUTH is that even Java is not truly platform independent when it comes to different operating systems. There are some technical differences that you'll need to look into. But for the most part of interactivity and high-level operations, yes, Java is more platform-independent than the others. But on a personal note, Java is my worst language. I try not to use it anywhere anymore. That's a different story.
In both options above, every client machine must have their own proprietory drivers and often some sort of API for browser integration.
A year or so ago, I had to program a Bio-Mini fingerprint scanner using VB. It was all sweet in the beginning. Then due to the restrictions of networkability and concurrent usage, the drivers/SDK could not take the load and things were going wrong. By the way, the drivers/SDK were meant for MS-Access. Knowing that the DB was the problem, I started to port this to MySQL. And it was a severe climb from there. I had to do a near-rewrite of the SDK for capturing and comparing data using arrays in VB. And to make things worst, the device was changed and things went wrong again. But do note that the new device was from the same manufacturer.
So keep in mind that even a simple change like that can cause a problem.
I'm using HttpBuilder (a Groovy HTTP library built on top of apache's httpclient) to sent requests to the last.fm API. The docs for this API say you should set the user-agent header to "something appropriate" in order to reduce your chances of getting blocked.
Any idea what kind of values would be deemed appropriate?
The name of your application including a version number?
I work for Last.fm. "Appropriate" means something which will identify your app in a helpful way to us when we're looking at our logs. Examples of when we use this information:
investigating bugs or odd behaviour; for example if you've found an edge case we don't handle, or are accidentally causing unusual load on a system
investigating behaviour that we think is inappropriate; we might want to get in touch to help your application work better with our services
we might use this information to judge which API methods are used, how often, and by whom, in order to do capacity planning or to get general statistics on the API eco-system.
A helpful (appropriate) User-Agent:
tells us the name and version of your application (preferably something unique and easy to find on Google!)
tells us the specific version of your application
might also contain a URL at which to find out more, e.g. your application's homepage
Examples of unhelpful (inappropriate) User-Agents:
the same as any of the popular web browsers
the default user-agent for your HTTP Client library (e.g. curl/7.10.6 or PEAR HTTP_Request)
We're aware that it's not possible to change the User-Agent sent when your application is browser-based (e.g. Javascript or Flash) and don't expect you to do so. (That shouldn't be a problem in your case.)
If you're using a 3rd party Last.fm API library, such as one of the ones listed at http://www.last.fm/api/downloads , then we would prefer it if you added extra information to the User-Agent to identify your application, but left the library name and version in there as well. This is immensely useful when tracking down bugs (in either our service or in the client libraries).
I have a small RIA that I built as a learning/make-my-life-easier project that uses Flex and ASP.Net. Currently, my architecture utilizes straight HTTP posts and the server responds with xml. I posted another question about security in my web app and some people mentioned SOAP. SOAP is something I've never actually used and I was wondering what the pros/cons were to using SOAP over my current architecture and then subsequently, how much work is require to convert such an application to utilize SOAP.
Thanks,
Chris
Since you have already implemented your own message schemas for sending and receiving, then SOAP in of itself will not give you any added value. The added value comes from SOAP's support for the WS-* standards, covering security, transactions, and several other goodies. The recommended way to take advantage of all that is to use WCF rather than ASP.NET, because WCF supports the latest versions of those standards.
FYI when trying to use SOAP with FLEX - XMLDecoder in Flex does not currently decode some complex data types appropriately, making it appear that you are not receiving all data. I have tracked the error down to the XMLDecoder where I can see the correct data is received, but is not appropriately packaged in the ResultEvent requiring me to override the XMLDecoder, which, I am sure you can imagine, is not very fun. Just wanted to put in my 2 cents. If you are thinking of moving in that direction it would probably be nice to know it doesn't always work for very complicated data types (in my example a collection of objects containing 2 strings and 2 arrays - only returns a collection of 1 string). Granted, it does work 99% of the time, but not always.