UDP Loopback adapter for testing?

[TyB]

I have a program that I wrote to send messages to PC on the intranet. It currently uses TCP which works fine. I realized that when I want to send a message to many PC that this can take awhile so I decided to use UDP broadcast in those instances.

I'm trying to add this function but I seem not be able to test it. In the TCP side of communicating I can set the IP to 127.0.0.1 and it works fine, but nothing on the UDP side.

Are you not able to use loopback with UDP for testing?

Thanks,

Ty

 

[TyB]

Also

In TCP I do not have to set an IP on the receiving app just the port it is listening on, but the UDP example I used shows that you do on UDP. Is that right?

That might explain the issue because I'm trying to both listen and send on 127.0.0.1 at the same time.

Ty

 

[JohnH]

With a UdpClient you specify IPAddress.Broadcast and the port to send to or receive from. There is no problem using two UdpClient instances in same application, where one send to a port and the other listen to same port (I posted one sample for this here), but you can do with only one also. Here is one quick sample:

Public Class Broadcast2

    Private udp As Net.Sockets.UdpClient

    Private Sub Broadcast2_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        udp.Close()
    End Sub

    Private Sub Broadcast2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        udp = New Net.Sockets.UdpClient(2456)
        udp.EnableBroadcast = True
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim ep As New Net.IPEndPoint(Net.IPAddress.Broadcast, 2456)
        Dim b() As Byte = System.Text.Encoding.UTF32.GetBytes(TextBox1.Text)
        udp.Send(b, b.Length, ep)
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        If udp.Available > 0 Then
            Dim ep As New Net.IPEndPoint(Net.IPAddress.Broadcast, 2456)        
            Dim b() As Byte = udp.Receive(ep)
            Me.ListBox1.Items.Add(System.Text.Encoding.UTF32.GetString(b))
        End If
    End Sub

End Class

This form has a Button, a TextBox, a ListBox and a Timer (500ms, enabled).

 

[TyB]

Do you have to have a gateway type app involved?

John,
I have been working with a chat type program code that uses a gateway app on a server that all the clients log into.

Is this the way it has to be? I was thinking from the reading that I could have clients listen on a port and then when I want to send a message from my server app that I just broadcast on that port?

Thanks,
Ty