The App that I'm working on has to load data from a webserver.
If I open the App with connected WiFi, it loads the data very fast. But it don't loads the data if it is connected to EDGE.
I don't know what I'm doing wrong.
Do I have to set something in the settings?
Greetings.
You shouldn't have to do anything specifically to turn on connectivity when using EDGE or 3G. It should just happen automatically. Not to state the obvious, but EDGE is pretty slow (probably 20-40kbps tops usable in normal situations), and often performs even worse than the theoretical speeds provided by the technology.
That said, using a neat little preference pane called Speed Limit, you can test your application in the simulator while simulating different bandwidth and latency constraints. You can get a better idea of the way you should expect your app to perform under EDGE with low bandwidth and high latency (or any other network connection). This will give you a better idea where your problem may lie and what to expect.
Related
I recently learned that GPU can do operations as CPU do, although there is tradeoff in the operation latency. Regardless the latency, can a GPU run an OS by its own?
Imagine a computer with no persistent storage, no user input, no networking and no sense of time/date. For this hypothetical computer, there's no way for anything in the real world (e.g. a user) to influence its behavior, and no way to tell if it has an OS or is merely showing a predetermined slide show.
In theory, if you can write an OS for this hypothetical computer, you wouldn't because there's no possible reason to bother. This describes a typical "GPU + video card memory" scenario (where a host OS running on the CPU is the only means of influencing the work done by the GPU).
Now imagine a "GPU" with various devices attached to it (some persistent storage, some networking, something for user input, a graphics card, ...) so that the "GPU" is able to manage (and abstract, and maybe even allow multiple programs to securely share) these devices. In this case, the "GPU" has become a central unit that does processing (a CPU!). It'll probably be a relatively awful CPU (with poor flow control and over-powered SIMD), but it's no longer a GPU.
Can we run OS in a gpu only device?
I don't know. If a tree falls in the woods, but nobody is around to hear it, does it make a sound?
I'm looking around to find the appropriate technology to implement an app that I've in mind.
Basically I am using bluetooth to estabilish a connection trhrough 2 iOS devices. In the first part of communication I only send messages, and everything works ok.
In the second part i would like to permit the user to share a video file; let's assume, for example, that the video file is 20 MB.
Now, what's the best option to transfer this large data through the 2 devices?
Can I use GameKit and split the data in small packet? It'll take a reasonable amount of time?
Or it's better to use Bonjour and wait that until the user'll be under the same wifi network or create a wifi network through the 2 devices?
Thanks in advance
In case someone else (like me) stumbles upon this question, I'll share my experience:
Bluetooth
Pros: You don't need wifi
Cons:
Apple only allows you to access the BLE interface, which is a lot slower than regular bluetooth. I tried this and it takes around 5 minutes to transfer 1 MB of data. Also, you need to chop your data into chunks of ~20 Bytes and make sure the files are received correctly on the other side.
GameKit
I haven't actually tried it, but it seems GK is fine to send small text messages (since it is designed for this), however sending larger files will still be pretty slow. Also, you can only connect 8 devices simultaneously.
Bonjour and Wifi
Pros: This is as fast as it gets. You can send reasonably sized files (a few MB) within a few seconds.
Cons: You need to be in the same wifi network.
Using a remote server
Pros: Assuming you have a decent internet connection it's reasonably fast and you are not depending on wifi (if you have 3G/LTE).
As it turns out this is pretty easy when you use a Backend-as-a-Service provider like Parse.
Cons: Well, you're gonna have to write that server software... Your app users probably need a mobile data plan.
I ended up with solution #3, using Bonjour and Wifi, since I didn't want to write server side code. If you want to do this, you need to learn about Socket programming. I suggest using CocoaAsyncSocket which uses TCP so you don't have to make sure you received the file correctly.
Since it is 2016 and Swift can be used in Obj-C projects, you can have a look at my solution, which will spare you almost all of the work: https://github.com/JojoSc/OverTheEther
It allows you to send any kind of object (implementing the NSCoding protocol) to another device.
We are in the process of developing an method of caching so that our app can continue to operate in an area with very little/no signal.
Obviously users will try to continue to use functions that require data and we need to handle the inevitable failure of these requests appropriately.
Essentially we are sat in the office, switching airplane mode on and off to simulate entering/exiting signal then adjusting our app to fix any issues this may arise.
What I'd like to know is, is using airplane mode going to give us a reasonable simulation of entering/exiting an area with no data or are there other implications?
I've seen questions raising the issue that the 3G/EDGE connection may not always wake up after airplane mode is switched on - while I appreciate this method is no way as good as actually being out in the field testing, if we can get a reasonable simulation and account for the majority of the problems that arise then I think this is an acceptable tradeoff.
I apologise if this has been asked before, I did do a search on here & on google but couldn't find any appropriate results.
You should try the Network Link Conditioner
There is a WWDC 2012 session called Networking Best Practices that mentions it (but he does not explain how to use it there).
To get it, you have to go to XCode/Open Developer Tool/More Developer Tools.. and download the latest Hardware IO Tools for XCode.
Once you install it from the IO Tools pkg, "Network Link Conditioner" will appear in System Preferences
You can then do something like 100% packet loss to simulate one of those routers that pretends you are connected but actually doesn't work.
On iOS, the network link conditioner is under Settings / Developer (you must have enabled Developer mode in XCode first to see it)
The main problem is that in the Airplane Mode the networking operations fail fast, while spotty mobile signal will lead to timeouts and a-few-bytes-an-hour speeds. This is usually a significant difference from the UI viewpoint. (It might be worth a try to use some bandwidth throttle to starve the testing machine and see how it behaves when the network starts to break?)
A few years back, when testing remote devices which used the cell network to communicate with the 'home base', we did things like move them into a shielded room (make shift), place large shields on three of four sides to force them to connect to a certain tower (and therefore, network), etc. Brute force physical methods. Since this actually cuts off the signal, it may be a more realistic approach.
You may also want to try this through your wlan-router. First, disable data roaming on your iPhone. Then, let the iPhone be connected to the internet through your wlan network. Then, disconnect the gateway on your wlan router while your iPhone is still connected to the wlan network.
This depends on what failure modes you are trying to test.
I use Airplane mode as a first pass check to make sure an app submission isn't quickly rejected.
Other network failure handling checks might include:
3G only (no wifi).
WIFI only (in Airplane mode).
Pulling the power cord on the WIFI access point.
Pulling the network cable from the back of the WIFI access point after connecting to it (Reachability may falsely say yes).
Walking in and out of a basement
elevator (or other Faraday cage) in the middle of a transfer.
Driving between 2 cell towers during a data transfer.
Walking between 2 enabled WIFI access points between connection and data transfer.
Starting the app after more than 30 minutes of device inactivity (radios may be idle).
Running the app while another app (Safari, Mail) is downloading in the background.
etc.
I have developed an application for iPhone, which is continuously interacting with database ... I have observed that it is running fine in 3G environment but in wifi its performance is not good.
Can someone suggest what can be the reason for it? or can I do anything to resolve it?
I'd rather expect the contrary, given that 3G cellular signal may fluctuate wildly, while WIFI signal should stay almost the same even if you move within the room served by the access point.
The reason may be the particular wireless connection you are using for testing purposes. Try using a different WIFI network and see if the behavior you are experiencing changes.
I was wondering what amount of time is required to convey information regarding the tilt and position (not gps) of one particular iphone to another. Could 2 iphones send and receive this information simultaneously? What about 3 iphones? I'm interested in an application that is able to simultaneously send and receive and make conditional decisions based on this information received all within a half a second-ish.
Any shot this is possible? If so, is bluetooth or wifi better?
Thanks a ton,
Jake
This is currently not possible without an intermediate server. (Without a jailbreak, which would make it possible, but extremely difficult)
I'm assuming your purpose is gaming, in which case, the latency associated with a trip to a server and back over a cellular data network, is likely to take too long for any satisfactory gaming experience. I don't believe it would be within half a second.
This will be possible via Bluetooth in the upcoming 3.0 iPhone software, but that is still under NDA, so you are not likely to be able to get any reliable performance numbers until it is released. If I were guessing, I would certainly guess that the latency associated with a direct Bluetooth connection would be FAR under half a second.
All you've got as an option right now is Wi-Fi or the Cell Network. If you use Bonjour over Wi-Fi, you'd have latencies in the milliseconds, but all the phones would have to be connected to the same access point. Take a look at the WiTap example.
It is definitely possible, you'd want to connect your peers over WiFi for best performance and reliability, but Bluetooth would be ok as long as your data packets were constrained to small sizes (< 1k). Check out this documentation and sample code to see how to access UIAccelerometer:
http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIAccelerometer_Class/Reference/UIAccelerometer.html
http://developer.apple.com/iphone/library/samplecode/AccelerometerGraph/index.html#//apple_ref/doc/uid/DTS40007410
The trick is that the update frequency is controlled in part by the systems needs, so there may be a window (while the system is attempting to update device orientation) wherein your application receives no updates.