I have created database in one application and that application is installed in multiple devices.My requirement is that if i change the value in database of one device then,that changes in database should reflect in another device of same application.I need it without server/third api.
Thanks in advance...
This is precisely when one does need a sever.
Stop and consider what it is that you are asking for. You need a way for a phone to notify all other phones that hold the same application about a change. Phones are not directly addressable to each other via the web, which makes any kind of peer to peer algorithm tricky. SMS texts is the closest form of direct addressing that phones do support, thus it could be used to build a peer to peer protocol, but that would be tricky, unreliable and is unlikely to be beneficial.
A server on the other hand is the standard approach to solving this problem, the server acts as a shared agent that all phones that connect to the web can address easily. Even if the server is just an FTP server on a freebie hosting site.
You need to implement a server functionality in your android application.
What is a server : A server is a running instance of an application (software) capable of accepting requests from the client and giving responses accordingly. Servers can run on any computer including dedicated computers, which individually are also often referred to as "the server".
For further information,I would like to provide this link which will clarify you about communication between two devices Android - communicating between two devices (Use of bluetooth etc.)
Related
Here is the current scenario:
I have two(2) Android phones.
Android Phone 1 as the server phone.
Android Phone 2 as the client phone.
Here is what I want to do:
I want to create an Android-based app (E.g. Student Information app) where it will have basically two (2) modes:
Server - for adding, editing and deleting data on a local database.
Client - for viewing data from the database of the server.
The app will be installed to Android Phone 1 and set to Server mode.
The app will be installed to Android Phone 2 and set to Client mode.
I want to ask these questions:
I want to locally host the database of the Server app, so that Client app will be able to view the data. Is this possible?
If yes, how can I do it?
Note:
I am currently a web developer so I know that connected on the same network is a requirement.
I have implemented the same concept on a medium business where the web-based system is locally hosted so that computers on the same network can access it.
Suggest everything that you want to suggest, except the disadvantage of doing this concept. I am aware of some obvious disadvantages based from my research and willing to face the disadvantages provided that I will be able to implement the concept.
Rooting the phones is an option.
I want to accommodate small-sized business that is why I want to use Android phones rather than using Desktop Computers/Laptop.
I have read similar suggested questions here based on my title.
We have done the exact same thing in my company. The way we solved this is that the server exposes a service using the Android NSD API, so the clients (using the same API) can find it on the network. And after a client has connected to the server, the server sends its database file (yes, the .db file in /data/data/...) to the client via OutputStream. When the client receives the entire database and checks for its integrity, it copies it to its own /data/data/... and restarts part of the app.
Android NSD
i am developing a chat application for local environment where our office employees can chat easily so here I am getting some conflicts when I am trying to send message over the IP but there IP being change dynamically so how can i resolve it .
First of all, I recommend using a well established solution like a local Jabber Server installation and using a client that supports the required features.
If you really want to pull this off on your own, you'll need at least a central controlling point (Server) to abstract Users from their Endpoint.
Configured user would then have to login to that server to signal they are ready to receive messages. Doing this, you have the momentarily correct IP that you can then use to relay messages or to give to other clients wanting to send to that user. Also consider that users may want to use more than one client (they have 2 PCs?). You probably wouldn't want to bind one user to one client device.
Also note that you will have to create a decent protocol for all this. This can be quite tedious if you want similar features to for example Skype Chat or ICQ, or some derivate of XMPP / Jabber.
This leads me again back to my first suggestion: Better use something that already exists. Installing and configuration of that can already be effort enough. Coding all that by yourself, though will take way more effort.
And I didn't even go into status/statusmessages, groupchats, sending/sharing Files, sending messages while User is away/offline ...
After a lot of research i am more confused then before on what kind of server to use for an android app.
My question in a nutshell is: which kind of server is easier to use and deploy.
I want to create an android application that communicates with a server to find other clients, the server uses GCM to notify other clients that one client wants to communicate and is used to exchange the address of the clients. Afterwards the clients should be able to communicate directly to one another.
What i found out is that from the android point of view either would be fine, both is likewise possible and neither produces more work then the other.
On the server side it looks like web service would be better to use, because it is easier to find a server provider. I might be wrong here but it looks like most large server providers don't like to give you enough access to run a jar file.
Google and amazon offer servers that can host web services, i am not sure if a socket server would be possible there, so if anyone can give me some tips on good and affordable server providers i would also like to have some insight there.
when building a server, one sometimes performs asynchronous tasks from client to server (which responds to client in asynchronous time),
or the server needs to send the client a message
now if the client is listening at all times (meaning polling) it takes a lot of resources which is problematic
here is where I assume the operating system steps in and assumes the role of polling for the appropriate port, and letting the application know using the appropriate event (the application subscribes using the OS API)
am I right in my assumptions?
how do I subscribe to a port using the OS's API? (lets say android for the sake of argument)
how is a message from server to client work exactly?
and how does the server know the client's IP at all times?
I have seen many questions in the subject, but wasn't able to figure out the big picture
Edit:
I am using GCM in android, but have seen other apps that does not use it and still manage to do it right, also it's a more general question as to what is the right approach in java VS. any operating system it uses (ubnutu, windows, android, etc.)
Totally right - polling is typically a waste of resources. Until recently, many apps would either keep a socket open and poll every few minutes to keep it alive, or make periodic HTTP calls to a server.
Nowadays, Google Cloud Messaging is used by most apps to push data instead of constantly polling. As you correctly guessed, this is implemented by maintaining a persistent connection with Google's servers. The advantage of this is that it's very efficient for battery life, and that all apps can use this one resource to send push notifications, instead of each app having to poll a different server or create its own persistent connection.
The idea is that you send requests to GCM from your server (this can be in response to user activity, etc), which sends it to all of the client's devices. You can either send a message with a small payload (up to 4kb) or a "send-to-sync" message, which tells an app to contact the server (e.g. to sync new data from the server after user changes).
here is where I assume the operating system steps in and assumes the role of polling for the appropriate port, and letting the application know using the appropriate event (the application subscribes using the OS API)
GCM pushes messages to clients, so there isn't active waiting like you'd see in a simple polling system.
how is a message from server to client work exactly? and how does the server know the client's IP at all times?
There's no need for servers to know the client IP, as any online android device will typically maintain a connection with GCM. Targeting specific users is done via User Notifications.
(Oh, and I realize that your question is more general than just Android, which I have more experience in, but iOS has a similar system in place. Some developers I've met like to use Parse for managing push notifications).
I'm currently building an application that is about VOIP / random chatting, which is similar to skype or chatroullet. My question is extension to this
https://stackoverflow.com/questions/11384155/running-java-server-application-24-7-not-on-local-machine
I've been experimenting and playing around with TCP / UDP sockets and now I have ability to build VOIP / instant chatting applications. But as you might already know, in order for data transmission between client to client or client to server, the server application has to be powered on (in other word, be online) and be accessible by client applications. The problem is that, I'm not living by my self but with my family, which I can't simply use one of my computer to run my server application for 24/7 mainly due to the electricity bills and my lack of knowledge about the networking concerns me about the security, because I had to go through some configuration / port forwarding on my current router in order to make the protocol accessible by other users outside of my local network. So my biggest question is that, how do people or developers normally have been dealing with this kind of situations? Have they been simply using their own computer to run the server application? or have they purchased an external machine to run the server application
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Additional question:
Is TCP / UDP socket the only way of making applications such as MMO, VOIP and instant chatting programs?
i see that your topic was closed in the previous thread. I think such questions are unrelated to stackoverflow.
However, i would like to give you a glimpse of what is happening to most of us who own / make Java Web Applications. I used to work in a datacenter for a year and a half. Java applications are a little harder to put online as they require resources that not many data centres are willing to invest time and support in. Other than that, they are pretty much as straightforward as normal PHP applications.
You will need the standard options like Colocation, Dedicated Server, VPS, Cloud Virtual Machine, or a shared tomcat / application server hosting.
Colocation is where you put your own purchased and configured server with the data center, you have complete ownership of the server, nobody can touch it unless permitted by yourself. You pay to put your server into the data center, and are in charged of anything that happens within the server, including OS patch.
Usually servers in data centers (due to size constraint) come in rack units. 1U refers to 1 rack space, usually this is equivalent to one PC, although a server is much more powerful. In Singapore, the charges per U is SG$200.
Dedicated server is where you lease a server from the data center. The server is managed by the data center and can be as powerful as you want it to be. OS updates, installations, service guarantees are provided by the data center.
VPS is having a fraction of a server resource, but many challenge that you do not have the "root" access to the server in most cases.
Cloud is the virtualization of the entire operating system. If this was Linux, you would have the root access to it. Many of us now are going for this option because of its scalability. Some data centers may use popular virtualization hypervisors like VMware ESXi, Microsoft Hyper V.
The list above is represented from the most expensive to the least. Of course, that is depending on your location and service provider.
Hardly anybody i know tries to put a running server at home, it is a fire hazard itself, you will not know when your electricity will be cut off, standard dedicated bandwidth would as expensive.
Hosting with a data center would be much cost efficient and safer in my opinion.
EDIT:
Is TCP / UDP socket the only way of making applications such as MMO, VOIP and instant chatting programs?
Have you looked at HTML 5 Web Sockets, or any AJAX based framework for this?
Try searching the web for cloud hosting. For example, Heroku, AWS and many others provide a hosted service. That is what people use to host their service and it is more cost effective than trying to maintain something yourself.
Are you writing an Android application for it as well? Just as an aside you might want to make use of this ARO tool to ensure you are using the network efficiently. http://developer.att.com/developer/legalAgreementPage.jsp?passedItemId=9700312