I use node.js to develop app, I want simulate some bad internet situation when people surfer on the internet,
like limit the data transfer speed, or delay some css or js file transfer
How can I achieve these goals?Is there some goal can do this?
I have used fiddler in the past to test unstable/slow internet connections on my apps. Fiddler has a modem speed option. Set that and you get incredibly slow speeds. You can also download a plugin called Delayed Responses, it will delay the packets from arriving back at to your app.
If that isnt up your ally, then I would suggest looking for a web based proxy that will allow you to control the parameters of the requests you want. Just google it.
Related
I am sure that this question has already been answered, but unfortunately I do not know the keywords. Therefore my search remained unsuccessful until now.
Scenario: I want to transmit a lifestream via Mobile Internet using RaspberryPi, and depending on the bandwidth, downscale the streams and upscale them again when available.
My two questions for the network specialists among you:
i know i can actively check the bandwidth, but how would you do this without interfering with the existing processes transmitting? Should I commit a bandwidth to the processes and then slowly determine the remaining bandwidth using a test tool? Or are there already practical solutions?
Can I determine in the mobile Internet, or in the network interface, when a bottelneck is reached?
Passive methods would be my preference. where I wouldn't have to load the bandwidth. e.g. I could know how much bandwidth the stream uses, and how much arrives. But how do I make sure there is enough capacity before I go up with the bitrate?
Thanks for your wisdom ;)
I am trying to create an app to mirror my phone's screen in a e-book reader's browser.
The idea is to continuously make screenshots and make them available from http server running on the phone.
So far I have succeeded in having an http server running on the phone and sharing the latest screenshot.
Now I would like to update the image in the browser automatically - which mechanics should I use - should the website pull the image every x milliseconds or can I push the changes from the server? The image transition should happen smoothly. The e-book's browser is somehow limited, for example it doesn't support html5-video and probably many other things.
I am using the basic dart httpServer (because my app is in flutter) and would prefer to keep it basic.
For testing I had a png Screenshot, but I would also like to optimize for greyscale and maybe try to do something with canvas (don't have experience here) if the browser supports it.
Main questions:
-is there an easy way to push changes from server to browser?
-how do I achieve a smooth transition between images (and skip refresh if the image didn't change)?
-which alternatives are there to using images?
-can canvas help me somehow?
I think the best thing to use here is WebRTC. The browser provides getDisplayMedia that allows you to either capture a tab or the whole display of a device.
You can then connect your two devices, and stream the capture live. The other nice thing is that it will be P2P and you should see sub-second latency (and you don't have the added complexity of running a HTTP server).
All you need is a signaling server to send the Offer/Answer/ICE Candidates between the two peers. These messages are just 'bootstrap' details to get the call started.
If getDisplayMedia doesn't work on the device you can add WebRTC via a native app. flutter-webrtc is one possible solution.
I need to perform a load test with 200+ concurrent devices on the android and ios apps. Is there any tool that can do that?
It depends on the network protocol(s) which your application is using for communicating with the backend.
You can identify which protocol(s) are in scope by installing the application into Android Emulator or iOS Simulator and use a sniffer tool like Wireshark to capture the network traffic.
Once you figure out which protocol(s) are being used you can choose a proper load testing tool which supports this(ese) protocol(s), an example comparison of free and open source load testing tools can be found i.e. in Open Source Load Testing Tools: Which One Should You Use? article
After you decide which tool you will be using you will need to replicate mobile device traffic using the tool of your choice to 100% match the network footprint of the mobile device (you might need to perform parameterization of credentials and correlation of dynamic parameters) and as soon as it will be done you should be able to replay the requests with increased number of virtual users.
Try AWS Device Farm they have a lot of configurations, devices and global options for testing.
Typically
you capture the device network requests using a proxy (we use charles proxy) as you are functional testing the app
Take out static resources, css, images, scripts (which are served from a cdn) and third party resources
then parameterise the dynamic requests to create a load test script
While you are perf testing, monitor navigate through the app to see the end-user impact when the back-end is under heavy load.
Yes, there are many solutions. The governing factor is going to be the communications model between your handheld device and the application/system under test.
In most cases (but not all) the protocol for communication is HTTP. In this case you may leverage a proxy for recording the conversation between client and server to reproduce the conversation of a single session. You may then modify this session to address dynamic server data for session, date, time, account information and user inputs. Once that is done then you may replay 200++ session representing the load of 200++ users on your system.
I would recommend a network simulator be involved in your test. Mobile networks are particularly dirty, leading to higher error rates and longer latch times (protocol, layer 3) on sites. Having the impairment from the network simulator will better allow you to understand the response times for your client. Look for impairment solutions which can ingest OOKLA data for various locations and times of day matching your high load windows.
I am writing a remote server to control a robot with. The robot provides video and its current sensor state; the server sends control commands.
My choices for sending the frames and the control/sensor-state between the robot and the server ( 2-way ) are ZeroMQ and WebSockets.
I need:
Speed
Security
My coding partner wants to use Websockets because it's undergoing standardization, but I have 3 months of experience using ZMQ to do just what we're trying to do, so I'm fairly certain the choice doesn't matter.
However, I'd like to know if anyone can think of a compelling reason to go with one OR the other (XOR). We're not going to use ZMQ+Websockets because we don't need to.
Looking at what WebSockets are, I honestly don't think it's going to make much difference. They're simply a way to switch between speaking HTTP to the WebSocket framed message protocol down the same TCP connection. ZMQ gives you framed messages too, but you'd be using that over a network connection separate from the web browser's HTTP connection.
Latency comparisons are going to depend on just how good a run time environment the Web Browser provides. It seems to me that use of WebSockets will involve writing the client side code in Javascript and running that in the browser (the "modern" way), so that code will be at the mercy of the Web browser's Javascript engine (they're pretty good I think).
With ZMQ you may be having to write a native application for the client end (I don't know if it can be used within a web browser within Javascript - I need some education!). A native application is free of any influence from a web browser, so it might be just a shade better.
But if your real time requirement is only on the human scale (i.e. it need respond only quick enough to make a human happy), I think either will likely be sufficient. Neither can overcome propagation times across the Internet, neither can account for OS / browser delays.
The one difference is that with WebSockets it looks like you have to switch between HTTP and WebSocket protocol. So if you need to switch back to HTTP to load some web element or other, that's going to interrupt the flow of WebSocket data until you switch back again. Whether or not that is actually a problem is going to depend very much on what your client side application is doing (for example, you may very well be talking to a separate web server for web page elements, in which case you'd have two connections on the go anyway).
With ZMQ you're going to have a dedicated connection.
I am trying to simulate user load on a hardware router. I am specifically trying to emulate the average load of a home router.
What i need to to do is load it up over a week long period at different times and perform the following:
Data Transfer
Torrent Downloads
HTTP/HTTPS Pages requests to different pages. Static content, dynamic content. etc.
I would need to this repeat at my specific intervals and be able to test multiple routers at once.
Anyone know of any software or scripts that will achieve this.
Cheers
Sure. You might be surprised to learn that the load on an average home router is probably pretty low most of the time. Do the math: even downloading at maximum DSL or cable router speed (even if it were small packet sizes, which in higher loads is not usually the case) is just not a significant load on a modern CPU these days.
Scripting loads is easy. I have a script that I bang against Comcast sometimes when I doubt their last mile link to my home. It simply uses wget (or try curl) to download a file of reasonable size repeatedly and records the download statistics (time and/or data rate) of the transfers. Just find a .pdf or other file of the size you need from around the net somewhere, or use a busy website with lots of content. Just avoid the little guys who might have to pay for that bandwidth you are consuming in your test. Better yet, Amazon S3 storage (and transfer bandwidth) is very cheap these days and easy to use. You could put some files of your own choosing up there, and download those repeatedly for your test environment instead of stealing bandwidth from someone else! ;)
Never played with any torrent clients, so I can't help you there, but I bet there are some you can script.
Also, you might check out netperf. I don't know the status of that project, but I've used it in the past to generate very high network loads. Google for it.
Have fun and good luck!
-Chris