Develop Reference

Android: Pure P2P chat application

I've started to develop a chat application for Android. This app is supposed to function without internet and, most importantly, without an access point; It has to connect Android devices in a pure P2P manner.
However I've followed the following tutorials posted in android developers guide:
http://developer.android.com/training/connect-devices-wirelessly/nsd.html
http://developer.android.com/training/connect-devices-wirelessly/wifi-direct.html#fetch
Afterwards, I've tested my app on 3 devices, the problem is one of the devices acts as an access point, preventing other devices from connecting with each other if they are connected to it.
This doesn't work for my app, because I want each user to be able to connect to multiple users at the same time.
What do you suggest I do in order to achieve pure P2P connection for my Android app?
Does the group owner acts as an access point?
EDIT
After I've done some research I found the WiFi Direct is not suitable for my project since it has to assign a device as an access point, what I'm looking for is WiFi ad hoc mode or (IBSS) in Android Anybody got any suggestion on how to start working on that?

By using bt and wifi simultaneously, you can try to extend the network further. This will require some kind of packet routing.
Also, it seems android ignores wlan cards connected to usb otg - just plugging in extra wlan dongles could allow easy extension of network.

Android to iOS connect via WiFi or using Multipeer connectivity or using WiFi direct

So I am developing an APP and I need to connect multiple android and multiple Iphone to send text data without any internet connection or service provider data network.
So one of the phone will have to act as a server to relay information between them. But the app will have to decide which phone will be the server and if a phone that is the server leaves the conversation then another phone will pickup as the server this will all be done with some smart programming but before I get there.
I know Android WiFi direct can do a one to many connection setup which makes it easy to connect android phone and accomplish the task between android phone only. But the problems comes when I need to connect Iphone with the android phones. Since the Iphone must be able to act as a server as well.
I would like to know a few things:
Can I connect Android and Iphone via WiFi Direct?
Can I connect Android and Iphone using Multipeer connectivity feature on Iphone?
Is there anyway to create a soft access point using Iphone? I know android can do this via WiFi direct feature.
If non of these can work can you suggest something.

From the discussion here it doesn't look possible
I wonder though if both OS allow enough control over the WiFi transceiver if you couldn't just write an app that could what you are asking and just bypassing the built in software architecture all together. I would think Bluetooth would be too weak except in extremely dense device saturation environments, but just for proof of concept that could be another route to take. My guess though is that you just wouldn't get that level of control over any of the radios inside a phone through the current OS.

Convert application using wifi to application using bluetooth

I have an android app, it does the following:
Connects with a server to read and update a database at the same time as others.
I want to convert this to an app that does not need an internet connection. Therefore i would like to know if its possible to have an android device acting as the server with the database, whilst multiple phones connect to it via bluetooth getting and updating the information in the database?
Thanks

Yes. It possible.
However all of your devices will have to be located nearby, so they can connect to each other through bluetooth.
You can take a look at Android Bluetooth API.
However, my recommendation would be to use Wifi instead of Bluetooth. YOu will need additional WiFi router. However, you won't need to deal with Bluetooth API in such case.
You will only need to write a server on one of Android device and the rest of devices will work the same (as now)

There are a few options to doing so, that don't involve a server. Both of them require a slightly different approach than both devices connecting to a server.
Wi-fi Direct- Only available with Android 4.0+.
Bluetooth
Personally, I have been using the Bluetooth option, and not found it terribly difficult. Essentially, you have to do the following to make it work.
Have one of the devices listen for a connection. If it is unpaired, you will have to make the device discoverable.
The second device needs to initiate a connection. It can do this by looking at the known devices and trying to connect to one, or listening for a new device
After the two devices connect, they must initiate some kind of a communication protocol. The communication is essential a serial connection.
Blue-tooth requires that the devices be within about 10 m of each other. Wi-fi direct will allow somewhat further, but as mentioned, is less supported. It is possible to allow for both communication methods, but is somewhat challenging.

Android - communicating between two devices

What is the best way for an Android app installed on two devices to communicate with each other? Can the devices connect directly without using text messaging?

You have several options, depending on your requirements and setup:
If your devices are very close to one another (up to about 10 meters), you can communicate using Bluetooth, as Derek suggested.
If your devices are somewhat further away, but within WiFi range of each other (up to about 100 meters), then they can communicate with each other using the Peer-to-Peer WiFi API, documented here (part of the Android Wireless API). This does not require a WiFi router to be present, and the devices will find each other and communicate directly. This does however require Android 4.1 or higher.
The Android Wireless API will also work if your devices are on the same local network (i.e., use the same WiFi router), even if they are not themselves within range of each other.
If none of these options are viable/guaranteed, then I agree with Derek that the easiest way would be to use ServerSocket and Socket to create a server/client interface through the Internet. Here is a sample application doing that. The main problem you might encounter is that if the server is sitting behind a NAT (such as a home internet router), you will have to configure the NAT to forward the incoming packets to your Android server.

You can connect them via bluetooth using BluetoothSockets. Android developer website has pretty good documentation on this.
http://developer.android.com/guide/topics/wireless/bluetooth.html
Or if you'd rather (and have internet on both devices), you can use regular Socket's.
http://developer.android.com/reference/java/net/ServerSocket.html for server side
http://developer.android.com/reference/java/net/Socket.html for client side
If you have a large amount of data to transfer, internet sockets have a greater data capacity and will be faster. The other advantage is that there is no such thing as "out of range". You can connect the two devices wherever internet is available, whereas with bluetooth they have to be within bluetooth range of each other

you can use PubNub. it handles all networking and you should only care about messages.
it has great API to work.
(Thanks to #Ian Jennings : Can we send data from an android device to another android device directly (p2p) without server in the middle?)

Depends on what you are doing. If you have a server, you may be able to send some message to it and have it pulled by the other device (assuming both clients have the app installed). I think this would be the most intuitive way (but it really depends on what you are communicating).
Text messaging and email might work, but you (or the user) needs to know the numbers/emails associated with a device to do that.

you should have a look at WifiDirect
Wi-Fi peer-to-peer (P2P) allows Android 4.0 (API level 14) or later
devices with the appropriate hardware to connect directly to each
other via Wi-Fi without an intermediate access point.

As was already suggested, sockets are the easiest way to accomplish this if your devices are all connected to a network.
There are things to accomplish here:
Use Network Service Discovery to find devices running your app
Connect to other instances of your app using a socket
For a complete tutorial you can check this out

ShortAnswer: Yes
Data can be sent directly.
In order of range:
1 Bluetooth
2 wifidirect
3 maybe.. GSM hardware direct?
After that, options again in range order:
4 tether or network
5 Internet

The android NSD API is meant to do the exact same thing you are trying to achieve! The example bundled with SDK is self explanatory!
please check:
Android NSD API example

How write a program to connect to a a2dp bluetooth device using pre 3.0 Android?

My application needs to connect to a a2dp device over bluetooth and I want to "be able to query for the visible bluetooth devices, then, select a a2dp device and have it 'connect via a2dp' so that audio starts playing through the connected device" but my phone is running gingerbread (2.3.3).
I went through the basic bluetooth tutorial at http://developer.android.com/guide/topics/wireless/bluetooth.html and got to the part I need to connect to the bluetooth device and then I read the bottom of the page:
"Starting in Android 3.0, the Bluetooth API includes support for working with Bluetooth profiles." -> does this mean that I am S.O.L.? Is there any way to programmatically (why does stackoverflow mark programmatically as being misspelled?!) connect to a a2dp device using a pre-3.0 version of Android? Is my only option to direct the user to go into their settings/pull up the settings programmatically?? Because I'm able to do it through the settings, I guess I just assumed it would be possible via my application as well.
Help?

Some of the Bluetooth classes (profiles like BluetoothA2dp) are hidden in Gingerbread. It means that their declaration is annotated by #hide, and they are not included into the SDK (Android.jar). This is done intentionally, since these APIs are likely to be changed in newer Android versions. Generally it is not a good idea to use hidden APIs, since your App can stop working on newer Android versions, but if you are sure you want to, follow
http://devmaze.wordpress.com/2011/01/18/using-com-android-internal-part-1-introduction/
Once you get access to them do something like (just a hint):
BluetoothA2dp mBluetoothA2dp = new BluetoothA2dp(context);
BluetoothDevice device = BluetoothAdapter.getDefaultAdapter().
// Loop through paired devices
for (BluetoothDevice device : mBluetoothAdapter.getBondedDevices()) {
if (device.getName().contains("whatyouwant")) {
mBluetoothA2dp.addSink(device);
}
}

So, after much more research, it seems that it is impossible to programmatically connect to a A2DP device on a pre-3.0 Android device. I am going mark this as the answer but, if someone finds otherwise, please correct me on this as I would really like to do it programmatically.