Passing data from socketcommunication to User Interface - vb.net

Question

In my current project I'm sending and receiving textmessages to/from a serversocket/clientsocket (TCP), much like a chat (My project is written in VB.NET). This works as long as I'm converting the bytes sent into strings and presenting them in a msgbox().
This code handles that part:
Try
client = ar.AsyncState
client.EndReceive(ar)
client.BeginReceive(bytes2, 0, bytes2.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), client)
Try
Dim message As String = System.Text.ASCIIEncoding.ASCII.GetString(bytes2)
MsgBox(message)
Array.Clear(bytes2, bytes2.GetLowerBound(0), bytes2.Length)
Catch ex As Exception
MsgBox("Error writing received message")
End Try
Catch ex As Exception
MsgBox("Error receiving message from server")
End Try
So far so good. However when I try to change "MsgBox(message)" into label1.text = message I get the error: "Error writing received message". My questions, then, is why this happens and what can I do to correct it so that I can have my sockets receiving information that can be added to textboxes and other things in the UI?
Thanks in advance for any help that you can provide

Answer 1

Use a delegate and BeginInvoke() to properly marshal the call to the main UI thread:
Private Sub OnRecieve(ar As IAsyncResult)
Try
client = ar.AsyncState
client.EndReceive(ar)
Try
Dim message As String = System.Text.ASCIIEncoding.ASCII.GetString(bytes2)
NewMessage(message)
Catch ex As Exception
MsgBox("Error writing received message")
Finally
Array.Clear(bytes2, bytes2.GetLowerBound(0), bytes2.Length)
End Try
client.BeginReceive(bytes2, 0, bytes2.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), client)
Catch ex As Exception
MsgBox("Error receiving message from server")
End Try
End Sub
Private Delegate Sub MessageDelegate(ByVal msg As String)
Private Sub NewMessage(ByVal msg As String)
If Me.InvokeRequired Then
Me.BeginInvoke(New MessageDelegate(AddressOf NewMessage), New Object() {msg})
Else
Label1.Text = msg
End If
End Sub