Using UDP and Winsock in Visual Basic 6 (VB6) to send a Broadcast Message

I had an application where I wanted an administrator to be able to send a broadcast message to everyone running a particular VB program on the local area network (LAN).

I’ve done a lot of VB programming in the past and a fair amount of TCP Winsock programming, but this was new to me and quite frankly took me way too long to figure out.

Here’s how I did it:

Create one VB Project, on the form place two items: a textbox and a winsock control

This is the “receiving” application.

On the form place this code:

Option Explicit

Private Sub Form_Load()

Winsock1.Close

Winsock1.Protocol = sckUDPProtocol

Winsock1.Bind 420

End Sub

Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)

Dim str As String

Winsock1.GetData str, vbString

Me.Text1.Text = str

End Sub

Private Sub Form_Unload(Cancel As Integer)

Winsock1.Close

End Sub

Create one VB Project, on the form place two items: a textbox, a command button, and a winsock control

This is the “sending” application.

On the form place this code:

Option Explicit

Private Sub Command1_Click()

Winsock1.Close

Winsock1.Protocol = sckUDPProtocol

Winsock1.RemoteHost = "255.255.255.255"

Winsock1.RemotePort = 420

Winsock1.SendData "lvmsg" & Me.Text1.Text

End Sub

Private Sub Form_Load()

Winsock1.Bind 420

End Sub

Private Sub Form_Unload(Cancel As Integer)

Winsock1.Close

End Sub

That’s about it. Just put whatever text you want into the text box and click on the button and it will be sent to the receiving application. Some of the details were missing on other web pages so I thought I would make it more clear here.