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Sending Broadcasts
 
Date: Oct 15 2000 
Subject: Online Programmer Ezine, Volume 1, No.1
Article: Sending Broadcasts with VB 6.0

Broadcasting is frequently used in local area networks.
If you want to send a message to all local computers you
can use broadcasts. Here we will discuss about broadcasting 
on TCP/IP network protocol.

For example if you want to find a resource on network you can
send a broadcast to all computers. Then computer(s) that 
contain that resource can answer to you.

You can find several applications for broadcasting. Just be
sure to use broadcasting whenever it is really needed. 

To send broadcasts you use UDP protocol to send packets to IP
address 255.255.255.255 and you can choose any port that is 
free on your computers.

Sending and receiving UDP broadcasts is very easy. You will 
not need a connect session for UDP. You just send and receive
packets. Also packet size limitation is related to your 
network devices but assume 256 bytes for maximum size of data
you send each time.

Below you see a sample program written in Visual Basic using
MSWinsock.ocx component. This component is the most stable socket
object I have seen until now. It is very easy to program sockets
with this object. I even prefer this object to native Delphi 
and C++Builder socket objects (Borland, Net Master and Indy) 
in that environments. 


   Private Sub Command1_Click()
    On Local Error Resume Next
    Dim str As Variant
    str = CVar(Text1.Text)
    Winsock1.RemoteHost = "255.255.255.255"
    Winsock1.RemotePort = 20480
    Winsock1.SendData str
   End Sub

   Private Sub Form_Load()
     Winsock1.Bind 20480
   End Sub

   Private Sub Form_Unload(Cancel As Integer)
     Winsock1.Close
   End Sub

   Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)
     Winsock1.GetData str, vbString
     Text2.Text = str
   End Sub

Form contains a command button and two text boxes.

If you want to write in other environment there is a Broadcast
Page at this address:

   http://www.angelfire.com/nt/sarmadys/page3.html



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