Share My Creation Simple Multi-User Chat Demo

Sooner or later somebody will want to know how to do this. It seems to be a fairly common "What next after Hello World?" sort of project.

The attached ZIP archive has two B4J programs: SimpleServer and SimpleClient.

While there is a huge amount I have to learn yet about B4J, these seem to be working properly. That doesn't mean they're bug-free or that I haven't done some things clumsily but these ought to be useful to help others get started with TCP sockets.

As provided these use ASCII for transmission with a CR message delimiter. You could easily change them to use UTF-8 and another delimiter or a length prefix instead.

There is a ReadMe.txt in the archive and I'll try to post a screenshot here.

 

[LucaMs]

Thank you, Dilettante (anche se io credo che potrei scrivere "Grazie" )

I need example like this (I have not downloaded it yet but I'm going to do it).

If you could convert it for BlueTooth and for PC to Android-device, I would avoid many headaches

Ciao e grazie


P.S. Sorry, Bob, "dilettante" is an italian word! lol

 

[dilettante]

It should be easy enough to convert SimpleClient into an Android version that interoperates with my Java SimpleServer using TCP sockets. Probably a little more work but not a lot to convert SimpleServer to an Android version.

To operate over Bluetooth the simplest thing might be to use a library containing a Java implementation of BluetoothSocket and BluetoothServerSocket, but I don't know whether such a library exists (either for Java itself or a even wrapped version for B4J to use). Android already has a Bluetooth Library that contains such classes, though I have not used it.

But I believe the custom here would be to create a question thread in order to get help with changes like this. It would probably bring in more people with specific experience using Bluetooth between an Android device and a Java device (such as a PC).

 

[Erel]

A chat example between PC and Android over Bluetooth is available here: http://www.b4x.com/android/forum/threads/jserial-library.34762/#content

 

[dilettante]

Thanks Erel.

That wouldn't really be multiuser (COM-port per Android device/user might work) but it probably addresses the needs of many people. The use of sockets is probably constrained by platform limitations, since I haven't found anything like the Android Bluetooth library for Java on Windows or Linux.

 

[LucaMs]

Yes, but I'd just need a conversation between pc and smartphone (without VB.Net or other!
Why I did not searched???

Thank you, Erel, this was for me the Christmas gift.

Thanks for your help, dilettante.

And again, happy holidays

 

[BPak]

Love the Chat Project, dilettante. Ran great on my Mac as well. Only thing I had to do is put a Client.jar in another location to get the second Client working.

 

[jmon]

Hi,
Thanks a lot for sharing with us. I have an issue, the server constantly drops the connection and I keep on getting the "#Server closed connection" message on the client side. Any idea what could cause this issue?

Thanks.

 

[dilettante]

Hi,
Thanks a lot for sharing with us. I have an issue, the server constantly drops the connection and I keep on getting the "#Server closed connection" message on the client side. Any idea what could cause this issue?

I haven't seen this. Are you using an unreliable WiFi or cellular data network or something? This is one of the reasons why HTTP 1.0 often works best for mobile clients: request, response, abandon the connection.

15 minutes (and counting), no drop-outs yet here.

 

[jmon]

I haven't seen this. Are you using an unreliable WiFi or cellular data network or something? This is one of the reasons why HTTP 1.0 often works best for mobile clients: request, response, abandon the connection.

15 minutes (and counting), no drop-outs yet here.

Thanks for your reply. I am on a LAN network. I will check if something else could be dropping the connection. I'll post again if I find something.

[EDIT] I apologize, your example works perfectly and doesn't drop the connection. I made a mistake when I modified your example in the "srvListener_NewConnection". I was setting the "intClient" to a wrong number and when new users where joining the conversation, they would be assigned to a wrong number and overlapping the old users, thus dropping the connection.
My bad!

 

[dilettante]

The important thing is that you resolved the issue so you can move forward.

 

[dilettante]

Love the Chat Project, dilettante. Ran great on my Mac as well. Only thing I had to do is put a Client.jar in another location to get the second Client working.

I'm still curious about this. On a Mac does the JAR file get locked so you can't run a second instance, or did I misinterpret the issue?

 

[BPak]

Not a Mac specialist but it just would not run a second Client from same location. Guess it stops it from running second instance.

However, when copying the prog to another folder it was allowed to run a second program of the same name.

I could test it more if required.?

 

[dilettante]

Thanks. I was just wondering what was going on that causes this on a Mac.

 

[BPak]

I tested it again on Mac Lion and it will only run one instance.

However Right-click the Icon for the Client and select Copy from popup menu and a copy of the client is created. It can be ran and used as the second instance.
I also tried using Right-Click and selecting Duplicate which did same as Copy.

Did search from Spotlight for 'run another instance of an application' and came up with a Web Search for Google and found a couple web sites that confirm the Mac is ONE instance only by design.

https://www.google.com/search?rls=en_AU&q=run+another+instance+of+an+application&ie=UTF-8&oe=UTF-8

http://reviews.cnet.com/8301-13727_...multiple-instances-of-an-application-in-os-x/

One says Copy as I have done. The other says it can be done from the Console

 

[dilettante]

Good to know.

 

[jmon]

Thanks for your great script. It works very well.

I sometimes have a bug that would crash the server. This fixes the bug:

Public Sub Close()
    astmClient.Close
    sckClient.IsInitialized Then
    sckClient.Close
    sckClient = Null
    mInUse = False 'switching this line
    CallSub2(mParent, mEventName & "_Terminated", Me) 'and this line
End Sub

I think you have to put the mInUse = False before the callSub2, because when calling the _Terminated event in the main module would still have this client registered as inUse = true and that could cause and crash the server if trying to send data to this client.

 

[dilettante]

Thanks, I'm sure others will find that helpful.