TIdUDPServer (and Client)

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6 total messages Started by Paul Sun, 28 May 2006 09:29

#2366

Author: Paul
Date: Sun, 28 May 2006 09:29

95 lines
3615 bytes

Hi,

I'm trying to get an idea of how Indy(9) TIdUDPServer and Client works and 
have created a small test application.

I have got the client sending data to the server, and this seems ok (the 
server event handler, and client thread extract is below).  What I don't 
understand or know how to achieve is the client receiving data back from the 
server.  I've not managed to get this to work so far.

Since the UDP protocol is connectionless, the read event must be at some 
mid-point in the process of receiving the client data.  So can the server 
only respond in read event handler, using the socket binding information to 
know where to return the data?

I've also noticed that when the server sends data, it receives its own data 
(when using 127.0.0.1 addresses for both ends).

Last question, if I want two PCs to communicate async, do I need both ends 
to be server and clients?

Paul


//---------------------------------------------------------------------------
// server form

void __fastcall TForm1::IdUDPServer1UDPRead(TObject *Sender,
      TStream *AData, TIdSocketHandle *ABinding)
{
    try
    {
        int BufSize = AData->Size;
        int BufIndx = 0;
        char * Buf = new char[BufSize];

        while (BufSize > 0)
        {
            int iRead = AData->Read( &Buf[BufIndx], BufSize );

            if( iRead > 0 )
            {
                // success
                BufIndx += iRead;
                BufSize -= iRead;
            }
            else
            {
                // fail
                BufSize = 0;
            }
        }

        // process buf
        Memo1->Lines->Add(Buf);

        // does not work???
        char msg [] = "Server: Testing Loopback UDP to Client";
        ABinding->Send(msg, sizeof(msg),0) ;

        // delete buf
        delete [] Buf;
    }
    catch(const Exception &)
    {
        ;
    }
}

//---------------------------------------------------------------------------
// client thread....

            if (IdUDPClient)
            {
                try
                {
                    char msg [] = "Client: Testing Loopback UDP to Server";
                    IdUDPClient->SendBuffer( msg, sizeof(msg) );

                    char rxd [100];
                    int  rxl = 100;
                    AnsiString peer = "";
                    int peerport = 0;

                    int len = IdUDPClient->ReceiveBuffer( rxd, rxl, peer, 
peerport, 100 );
                    if (len)
                    {
                        AnsiString str = len;
                    }
                }
                catch (...)
                {
                }
            }

Re: TIdUDPServer (and Client)

#2367

Author: Remy Lebeau (TeamB)
Date: Sun, 28 May 2006 19:35

34 lines
2174 bytes

"Paul" <plmacca@clara.co.uk> wrote in message
news:44796d7e$1@newsgroups.borland.com...

> I have got the client sending data to the server, and this seems ok (the
> server event handler, and client thread extract is below).  What I don't
> understand or know how to achieve is the client receiving data back
> from the server.  I've not managed to get this to work so far.

In the server's OnUDPRead event, you are provided with the IP and port of
the client.  Send your data to that IP/port.

> can the server only respond in read event handler using the socket
> binding information to know where to return the data?

Exactly.

> I've also noticed that when the server sends data, it receives its own
data
> (when using 127.0.0.1 addresses for both ends).

UDP data can appear on any network adapter that is installed.  Depending on
how you are sending the data and where, it is possible for the server to
receive its own data back.  It is your responsibility to look at the data
and ignore anything you don't want.

> if I want two PCs to communicate async, do I need both
> ends to be server and clients?

No.  The server is already asynchronous.  On the client side, simply use the
UDPClient in a thread so the main thread is not blocked.


Gambit

Re: TIdUDPServer (and Client)

#2368

Author: Paul
Date: Sun, 28 May 2006 20:26

4 lines
1126 bytes

Thanks.  I'll give it another go tomorrow morning.

"Remy Lebeau (TeamB)" <no.spam@no.spam.com> wrote in message 
news:4479fd0f$1@newsgroups.borland.com...

Re: TIdUDPServer (and Client)

#2369

Author: Paul
Date: Mon, 29 May 2006 12:00

23 lines
1564 bytes

Hi,

Spotted a mistake in my code, and with that fixed I've got UDP packets being 
received by the server and responses received back at the client.

I've also now moved both the TIdUDPServer and Client components in their own 
thread (each), and this seems to be ok too.

For now, final two questions:

1)  What does the property ThreadedEvent do for the TIdUDPServer component?

2)  How does the IdUDPServerStatus event get triggered?  I've had an event 
handler registered, but I don't get any events triggered?

Thanks

Paul


"Remy Lebeau (TeamB)" <no.spam@no.spam.com> wrote in message 
news:4479fd0f$1@newsgroups.borland.com...
>

Re: TIdUDPServer (and Client)

#2370

Author: Remy Lebeau (TeamB)
Date: Mon, 29 May 2006 17:23

20 lines
1730 bytes

"Paul" <plmacca@clara.co.uk> wrote in message
news:447ae24c$1@newsgroups.borland.com...

> What does the property ThreadedEvent do for the TIdUDPServer component?

Like most of the Indy server components, TIdUDPServer is multi-threaded.  It
uses a worker thread to continuously read data from the UDP sockets.  By
default, TIdUDPServer uses TThread::Synchronize() to trigger the OnUDPRead
event in the context of the main thread.  Setting the ThreadedEvent property
to true tells TIdUDPServer to not call Synchronize() so that the event
handler is called in the context of the worker thread rather than the
context of the main thread.

> How does the IdUDPServerStatus event get triggered?

There is no OnStatus event in TIdUDPServer in Indy 9.


Gambit

Re: TIdUDPServer (and Client)

#2371

Author: Paul
Date: Mon, 29 May 2006 21:40

9 lines
1306 bytes

Thanks.

"Remy Lebeau (TeamB)" <no.spam@no.spam.com> wrote in message 
news:447b2ea8@newsgroups.borland.com...

> Setting the ThreadedEvent property
> to true tells TIdUDPServer to not call Synchronize() so that the event
> handler is called in the context of the worker thread rather than the
> context of the main thread.

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