I wish to create an application that will hold a large amount of heavy data (images and sound files) - I wish to avoid having a heavy app. I saw that there are apps that you download from app store and only after they are on your device they download from a server the rest of the files.
I already started reading about JSON and it seems quite clear, but I have never worked with servers before.
Can anyone direct me to a good tutorial that explains how to create my database on a server?
Maybe some recommandations to which servers and tools are available? - preferably free tools...
You can use phpMyAdmin and mySql (both free).
You can find all the info you need to install phpMyAdmin here :
http://www.phpmyadmin.net/documentation/
And you will learn all you need for basic sql here:
http://www.w3schools.com/sql/default.asp
Related
I'm new to server side programming with a background in iOS. So I want to know where to start.
Here I tried to list some specific questions:
Can I just create a local database and practice on that?
Do the local databases and databases on remote server work the same?
If no, how can I choose which server I can use? (I went through the webpages of AWS cloud service and found they are really overwhelming.)
Arslan's answer is great, but I would like to add to it a bit. You mentioned a Chatroom, so in that case you should look into socket programming. The reason why I bring this up is, while no one has outright said it, you shouldn't create a chat server by read / writing to a database. It's much better to just keep it in memory and log to the database on an as need basis.
AWS is a fantastic solution and they have a lot of different solutions for different situations. You should look at using EC2, which is their server program. They have a free tier of it so that you can use and / or you can test locally. I suggest testing locally then pushing up to a free tier every now and then to make sure everything is running properly.
Also I would look into using CloudKit for data base storage. If you don't need instantaneous communication, it's far easier to use Apple's built in system rather than setup a server and manage it.
links: CloudKit, AWS EC2 Free Tier
As it happens I'm actually working on a ChatRoom Server program, here's the link to github. It is written in C++ so I recommend using it as a reference unless you want to write your own socket in C++.
Can I just create a local database and practice on that?
Sure. You can install a server locally on your machine ( there are plenty of available ) and through 'localhost:3000' or 'localhost' you can access the root of your server depending upon what you are using at server end. You can then configure your server to respond to a particular message.
Do the local databases and databases on remote server work the same?
Of course, the work they way is almost same. The difference you have stated yourself: remote.
If no, how can I choose which server I can use? (I went through the webpages of AWS cloud service and found they are really overwhelming.)
I would suggest you to start from the local server. But first you have to choose language: PHP, Ruby, Python - it depends upon you and your personal preferences. You can also use something like Parse.com. Parse.com is free up to 30 requests/second, and you can use Objective-C to send and retrieve data from the server with a few very easy steps. And of course, parse.com handles singing up and logging in a user for you , all you have to do is to write a code of few lines in your iOS app.
Download Apple's free Server.app from the Appstore, it wraps one of the best database management systems: PostgreSQL. Start it with this Terminal command:
sudo serveradmin start postgres
More info on these pages:
http://support.apple.com/kb/HT5583
http://www.postgresql.org
I'm developing a site-specific installation for an office lobby which will display content on 6 iPads. The installation has several megabytes of data which will be managed by a django webapp. I'm considering different strategies for fetching the content data from the web app. So far, I have simply been dumping the data in to xml format and fetching it via a single http request from the iPad to the content server. I then load all of the content in to memory on the iPad.
I'm beginning to have some concern that I may run in to memory issues as the amount of content grows, and that storing the entire database in-memory won't work. The natural next step is to think about a database on the iPads. I'm using sqllite for the content server. Seems to me that it may be feasible to simply download the entire database file itself and query it directly from the iPad.
Proposed Approach
Download the actual sqllite database file nightly from the django content server to each of six iPads used in an office lobby installation.
Things I like about this approach:
It could be really simple. It removes the whole web services layer from the system.
It protects against network problems nicely. If the network is unavailable, the worst problem is that the iPads display stale data, as apposed to there being no content if the system is network-dependent.
Things I don't like about this approach
I'm not sure how to safely download the file. How to I ensure that the file I'm downloading is in a valid state, and I'm not downloading while someone is updating it?
I've never heard of anybody doing this, or even considered doing it. It seems like it's far from tried and true.
My questions
Can anyone think of reasons why this is a bad idea?
How can I safely download a sqllite file with confidence that it's in a valid state?
Why don't you create a Syncing system - perhaps with JSON.
I've done something like this before - I had a central repository server on site that was running my Django web application. The different iPads would sync regularly with the web app's database making sure their local data matched the server data, if not it would update via json.
On the iPad itself, I was using phonegap's SQLITE syntax which worked perfectly for storing the clientside data. But the key was syncing this database via json to the central repositorie's database - rather than physically moving the SQLite db over to the ipad.
I want to create an app where clients connect to a server and communicate with each other via images and texts. I already have a server as backend, but is there any way that an iPhone becomes the server? I know that there is CocoaHTTPServer, but all of the examples are just a server displaying a webpage. Do you know how I can use it to fit my needs ?
There is no way to just take all you stuff that now runs on an apache directly to the iPone
You find a couple of tutorials and solutions in the internet.
Maybe this thread can help you: iOS devices as web server
Concerning CocoaHTTPServer
Maybe have a look at the SimpleFileUploadServer
I've seen lots of questions and answers about this topic, but unfortunately none of them seem to fit my needs closely enough. This question is about both iOS and vb2010.
I have created an app which communicates with my server (at this point, "my server" is actually my Win7 machine that I am using for development. Eventually it will move to an actual server). The back end is a VB program that interfaces between the iPhone app and a SQL Server database. A specific port is open to the computer, and everything there works great. I am able to retrieve data from the database and display it on the iPhone with the app, and also able to save records from the app to the database. It's all so very cool, and I'm really jazzed about it.
The final phase of the project requires uploading a camera image to the server. This is the part where it gets funky for me.
So far I have been able to save the image as a file on the iPhone's disk. Now I need to understand better how to transfer that file to a directory on the server.
I know that there are many techniques that use the "post" method, but as I understand it, that requires a PHP or ASP page to accomplish. FTP generally uses ports 20 and 21. What I would really like is to be able to set up the existing software to receive an upload request from the app, and then place itself in receive mode. This would not require opening another port, and I can tailor the VB code to handle the file however I like.
All I really need to understand is, how can I get the two programs to do the file transfer? And is it reasonable to assume that I can use the same port?
I want to know which is the best architecture to adopt for this case :
I have many shops that connect to a web application developed using Ruby on Rails.
internet is not reachable all the time
The solution was to develop an offline system which requires installing a local copy of the distant database.
All this wad already developed.
Now what I want to do :
Work always on the local copy of the database.
Any change on the local database should be synchronized with distant database.
All the local copies should have the same data in other local copies.
To resolve this problem I thought about using a JMS like software eventually Rabbit MQ.
This consists on pushing any sql request into a JMS queue that will be executed on the distant instance of the application which will insert into the distant DB and push the insert or SQL statement into another queue that will be read by all the local instances. This seems complicated and should slow down the application.
Is there a design or recommendation that I must apply to resolve this kind of problem ?
You can do that but essentially you are developing your own replication engine. Those things can be a bit tricky to get right (what happens if m1 and m3 are executed on replica r1, but m2 isn't?) I wouldn't want to develop something like that unless you are sure you have the resources to make it work.
I would look into existing off-the shelf replication solution. If you are already using a SQL DB it probably has some support for it. Look here for more details if you are using MySQL
Alternatively, if you are willing to explore other backends, I heard that CouchDB has great support for replication. I also heard of people using git libraries to do that sort of thing.
Update: After your comment, I realize you already use MySql replication and are looking for solution for re-syncing the databases after being offline.
Even in that case RabbitMQ doesn't help you at all since it requires constant connection to work, so you are back to square one. Easiest solution would be to just write all the changes (SQL commands) into a text file at a remote location, then when you get connection back copy that file (scp, ftp, emaill or whatever) to master server, run all the commands there and then just resync all the replicas.
Depending on your specific project you may also need to make sure there are no conflicts when running commands from different remote location but there is no general technical solution to this. Again, depending on the project, you may want to cancel one of the transactions, notify the users that it happened and so on.
I would recommend taking a look at CouchDB. It's a non-SQL database that does exactly what you are describing automatically. It's used especially in phone applications that often don't have internet or data connectivity. The idea is that you have a local copy of a CouchDB database and one or more remote CouchDB databases. The CouchDB server then takes care of teh replication of the distributed systems and you always work off your local database. This approach is nice because you don't have to build your own distributed replication engine. For more details I would take a look at the 'Distributed Updates and Replication' section of their documentation.