A few months ago I have coded a messenger program in C# which enables many clients to connect to a server and have a chat.
Now, I want to code the same program for android. After reading the bluetooth article in Android Developers, it seems that this is possible for a device to hold many bluetooth sockets at the same time + be discoverable (I'm talking about the server). The only action the said that should not work togather with bluetooth sockets is discovery, but since the client runs that, it doesn't change much.
But what made me unsure if it's possible to be done, is the fact that there is NO such an application in the android market! (Atleast not after a quick check.) There are many bluetooth chat apps, but none of them allows multi clients.
So before I begin coding that, I want to make sure it is possible, and make sure that holding, say, 5 tcp sockets won't kill the server phone.
Thanks in advance :)
Here is a link I found:
"Multi-device extension of the official Android Bluetooth Chat example"
Is that what you wanted?
Related
I am creating a multiplayer android game as a part of my coursework. This is my first game. I intended to allow users to connect to the game over a simple network. I don't want to use internet at all hence I wont be using the android game services. How do I go about this. I have no clue at all. I have tried various tutorials but all of them are using a central game server. I just want to create a simple Client - Server network. One user will host a game and others will join.
it's my first time answering a question here. I usually just read here in stackoverflow. I'm also currently working on my first game. It connects devices using wifi peer-to-peer or WifiDirect (without a wifi hotspot). It requires high version of android OS (4.0 or 4.1?) but I believe you can also try the other way on which the devices needs to connect in the same wifi hotspot for lower OS version requirements. The latter, I haven't tried yet.
After I connect the devices on the same network (peer-to-peer), I use sockets to exchange data between them. I use serializable objects for sending data. I don't know if it's the best way but it works for me.
My game can connect more than two players in wifi peer-to-peer. One device acts as the network owner (and also the game server).
See android's tutorial/documentation for WifiDirect connection :
http://developer.android.com/training/connect-devices-wirelessly/wifi-direct.html
Be sure to read also the adjacent lessons.
Also, Sockets must be used with Threads so you also need to read about it if haven't.
Hope I helped ^^
I finally got the solution and made the Android application. Simply used java socket programming. It works on Hotspot. This works on client - server framework.
Please find the code here and contact me if you require any assistance.
https://github.com/rohitramkumar308/GameOfCards
and this is the link to the app
https://play.google.com/store/apps/details?id=srk.syracuse.gameofcards
Hope this helps you.
Socket programming question here.
My interface comprises of an Android device(client), A wireless module hosting an access point, and an Arduino Uno(server).
My Android client class works when 1 user connects and sends commands to my Arduino server class.
I want to make my program friendly to many users at the same time. My server will only read in values from 1 connected client at a time.
After some research I've found that Arduino does not allow multithreading naturally, which is why i've decided to look into a number of libraries.
The Arduino library that I've decided to use for this specific issue is protothreads. Unfortunately, i've been unable to find any examples of creating a server with Arduino to accept a client's commands. Furthermore I'm having a lot of trouble figuring out how to make this library work in my favor.
Now for my question,
How exactly can I allow my Arduino server to constantly listen for
incoming messages from more than 1 client device?
Or is there something I can do on the client side that would make this communication possible?
Could you get away with accepting the socket responding and the closing it. Similar to a web page. As not to have multiple sockets open at once. Note uno only has 2k of ram flash goes quick. By one and close each stands alone and naturaly allow many different connections. Just one at a time.
I have a task to integrate a Bluetooth device into my application. Now my requirement is very specific. The device has a specific communication protocol which relies on certain ACKs but I figured it would make my development much easier if there was a program that let me test communication with the device.
I was wondering if there was a program for Linux, or perhaps a simple Android program which let me communicate with any Bluetooth device with a series of pings using data I enter and simply log the responses.
EDIT: I might not have been clear enough in my question.
I have a scale that I need to integrate into my application, and the scale has a protocol similar to this:
Get a specific byte string from device
Transfer data
Transfer packet for disconnection
Receive acknowledgement for disconnect packet
Disconnect
Now when I have to issue a POST request from my application, I usually build a test script online so I can test if the POST works properly.
I was wondering if there was something similar I could do with the device.
Thanks
Your question is not clear enough. To communicate with a BT device, you need to know what profile your device supports. Depending on that, you can find a way in Android or Linux or windows to communicate with the device.
The simplest way is to open an RFCOMM channel from android/PC and transfer data to and from the device. For this the device has to support the serial port profile (SPP). If you want to do this in Android, look for the BluetoothChat example from google.
If you want to use a PC/mac/linux look at the Bluez python module. It's really simple to use. There are plenty of other options too..
I was looking for something like SENA BTerm. It lets me connect to any device and send whatever data I wish.
It is an extremely useful tool for testing my code.
http://www.sena.com/download/manual_bterm/overview.html is where you can find it.
Is it possible to set up the Android Bluetooth Chat sample app to connect more than one person at a time, and have a mini chat room? What would that entail?
tl;dr version: Bluetooth sucks for this, don't use it, use wifi instead, probably backed by a web backend.
I have investigated this issue thoroughly throughout the years in the interests of a social wireless network research project. My general advice is: it doesn't work with more than two / three people. Bluetooth just isn't designed with wireless peer to peer networks in mind.
In general, it seems that the cheap Bluetooth controllers included on Android devices (especially HTC's devices, iirc) don't really handle any more than two or three connections at a time. I'm unsure if this is a hardware or firmware problem, but I can recount some basic anecdotes. I was working to implement this idea at the SDK level (i.e., without firmware modifications) around the beginning of 2011, and was able to get a peer to get two additional connections (i.e., three devices, each connecting to the other two) to work for a period of a few minutes to an hour before the connections would suddenly die and the socket would become unusable, requiring reconnection. Unfortunately, 20 minutes was an upper bound, and generally it was impossible to get connections to more than one other device at all reliably.
The goal of the project was to support multiple people interacting with each other silently in the background, but this never materialized, instead we ditched Bluetooth and went with wifi instead, which worked much much better. In the abstract, I think people view Bluetooth as a possible medium for reliable peer to peer communication, but it wasn't really designed that way: it's more of a medium used for short range communication between small devices (think headsets).
Be aware that if you want to do this, the maximum number of devices to which you can connect is fixed, because as per the Bluetooth spec, a piconet supports a maximum of seven devices. (See the wikipedia article.)
The required change is simple: you use a different UUID for each device. This can be implemented a number of ways, using an out of band exchange mechanism, or simple scheme where you assign UUIDs in an increasing fashion and when connecting to the network, try each in succession.
Here are some relevant Google groups threads:
Bluetooth peer to peer networks
Multiple connections on Android Bluetooth
I remember posting a more elaborate one detailing how to do this (with code) that I might dig up as well.., if I can find it. It should be from late 2010 or early 2011.
So the answer is, in the abstract, yes, you can try to do this, by using multiple UUIDs (after you use one, that's it, and you have to try another using some assignment protocol). However, in practice, after a lot of trial and error, this doesn't really work for what you probably want to use it for, and it's a lot better to go with an internet backend instead. By the way, this is also good for another reason, most users don't really like to turn on their Bluetooth for fear of their battery being drained..
Leaving this here, in case it helps someone else.
I was able to make my custom chat room following official bluetooth tutorial and modifying it a little.
Unfortunately, I cannot provide most of my code, but main idea is:
Every device is acts both as server and as a client. When Chat is started, device starts its server thread. Server thread is the same as official but doesn't ends when accept connection. It just keep listening.
Client thread is identical as in tutorial.
Both server and client thread manages connection same. I created separated threads for accepting messages following this tutorial and one for sending them.
private void manageConnectedSocket(BluetoothSocket socket) {
//create thread responsible for sending messages.
SendingThread w = new SendingThread(socket);
MainActivity.addSendingThread(w);
//Creates listener for messages to accept.
MainActivity.addListener(socket);
}
Now in main activity always when user click send button, for each worker (sending thread) send message to remote device. Listening is running asynchronously.
IMPORTANT:
You need to handle exceptions when message send fails and remove sending and recieving thread for device when you detect it is disconected. In my case I used well known UUID "00001101-0000-1000-8000-00805f9b34fb". For every device.
You need to wait 3 second between atempts to connect as client because some devices has weak bluetooth hardware and it is refusing connect as client.
Bt connection is supporting up to 7 -10 connections. So you will be limited in that range. I think it is designed for extensions of main device and not for random comunication
Source: search "bluetooth programming" on google
For my Android app, users need to connect to a server that will be hosted somewhere on the same LAN. There can be multiple servers hosted on the same LAN. To make it easy for the user, I was going to scan the current LAN that the Android device is connected to and then list all of the network devices that have the server running on it, rather than having the user input the IP to the computer manually.
I'm fairly new to networking, and after some searching I found out that I would have to use a multi-cast DNS search or UDP broadcast to detect the other devices. I also found a nice library called jmDNS, although I've found very few documentation and sample code on it. Could somebody point me in the right direction for what I'm trying to do to save me wasted time (mostly if I'm on the right track)? I'm assuming that I'll have to modify my server a bit to broadcast it's there? It works completely as intended if I input the IP manually into the configuration page on my app. Also, this only needs to discover Windows computers, not sure if that matters. Thanks in advance.
Well, jmDNS is a complete Java library that you could use for your setup. It can be used to braodcast your services which other clients can search for.
Bounjour service on windows is a bit tricky, although it's definitely possible. The easier way, I would say is to use jmDNS for broadcast and discovery for both your servers and clients.
You would run the jDMs or other service on your local area network as a background service or a dameon.