Android Question Wifi for several connections

[postasat]

Hello guys,

I need to exchange data (not file, only text messages) between one and several android device.

I have one android tablet and I need that act as a wifi server (without AP) to receive simple messages from every phone (client) connected in wifi to the tablet.

Is it possible ? Which is the limit number for client phones connected at the same time ?
How can I do ?

Thank you.

 

[Erel]

Are all devices connected to the same wireless network?

 

[postasat]

Hi Erel,

the best would be to create a wireless network where the tablet is the server (hotspot ?) without external wireless network.
To have the tablet and the phones connected together also in place where there is not a wireless network available.
If this is not possible, I could still use the same wireless network for all the devices (tablet and phones).

I'm using serial bluetooth (perfect !), but now I need to have a connection with more than 7 devices at the same time to send message from phones to tablet and I don't know how to find a solution.

Thank you.

 

[Erel]

There are two separate issues here:
1. Creating a local network.
2. Implementing the application level communication.

For the first one you will need to create a hotspot. Any device can create the hotspot. It doesn't need to be the server.

I recommend you to use MQTT for the communication. You can run the broker on the server (or any other device). This is the simplest way to communicate between multiple devices.

 

[postasat]

Hello Erel,
thank you for your solution, it seems perfect.

I installed the jMQTT library and jMqttBroker library.
I downloaded MQTT Chat Room example.
I added only this code in manifest editor (but without I have the same error)

AddPermission(android.permission.INTERNET)

I have this error during compile:

B4A version: 6.00
Parsing code. (0.02s)
Compiling code. (0.45s)
Compiling layouts code. (0.04s)
Organizing libraries. (0.02s)
Generating R file. (0.64s)
Compiling generated Java code. (5.34s)
Convert byte code - optimized dex. Error
warning: Ignoring InnerClasses attribute for an anonymous inner class
(org.apache.log4j.chainsaw.ControlPanel$1) that doesn't come with an
associated EnclosingMethod attribute. This class was probably produced by a
compiler that did not target the modern .class file format. The recommended
solution is to recompile the class from source, using an up-to-date compiler
and without specifying any "-target" type options. The consequence of ignoring
this warning is that reflective operations on this class will incorrectly
indicate that it is *not* an inner class.
UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already added: Lorg/eclipse/moquette/server/ConfigurationParser;
at com.android.dx.dex.file.ClassDefsSection.add(ClassDefsSection.java:122)
at com.android.dx.dex.file.DexFile.add(DexFile.java:161)
at com.android.dx.command.dexer.Main.processClass(Main.java:615)
at com.android.dx.command.dexer.Main.processFileBytes(Main.java:570)
at com.android.dx.command.dexer.Main.access$2(Main.java:546)
at com.android.dx.command.dexer.Main$2.processFileBytes(Main.java:514)
at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284)
at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166)
at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144)
at com.android.dx.command.dexer.Main.processOne(Main.java:537)
at com.android.dx.command.dexer.Main.processAllFiles(Main.java:449)
at com.android.dx.command.dexer.Main.runMonoDex(Main.java:236)
at com.android.dx.command.dexer.Main.run(Main.java:206)
at com.android.dx.command.dexer.Main.main(Main.java:179)
at com.android.dx.command.Main.main(Main.java:103)
1 error; aborting

Did I miss something ?

 

[Erel]

Please download the library again. It is fixed.

 

[postasat]

Hi Erel,

thank you now is fixed, I can compile.
I tried the example installing on a tablet (only with wifi) and in a phone.
I create an hotspot on a tablet and I have connected correctly the phone to the tablet wifi network.
When I setup the app in the tablet to be the server, the address is always 127.0.0.1, with the phone set as client I can't connect to this address.
If I use the tablet connected to my home wifi and create an hotspot on the tablet now the address is 192.... and with the phone I can connect and exchange messages.
Is it possible to change the address on the tablet not to be a localhost 127.0.0.1 also if the tablet is not connected to an external network ?
It will be perfect if I could use it creating a network with the tablet without connection to external wifi or data network.

Thank you.

 

[Erel]

By default the ip address of the hotspot device is: 192.168.43.1
Try it (even if it shows 127.0.0.1).

 

[postasat]

Perfect, thank you.
Now I can try to use this in my app !