Visual Basic

Option Strict On
Imports System.Windows.Forms
Imports System.Net
Imports System.Net.Sockets
Imports System.Threading
Imports System.Text
Imports DevExpress.XtraEditors

Namespace Forms
    Public Class Messenger

        Delegate Sub AddMessage(ByRef message As String)

        Private Const port As Integer = 33333
        Private Const broadcastAddress As String = "255.255.255.255"

        Private receivingClient As UdpClient
        Private sendingClient As UdpClient
        Private receivingThread As Thread

        Public Sub New()
            ' This call is required by the designer.
            InitializeComponent()
            ' Add any initialization after the InitializeComponent() call.
            AddHandler btnSend.Click, AddressOf btnSend_Click
        End Sub

        Private Sub txtMessage_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs)
            Select Case e.KeyCode
                Case Keys.Enter
                    btnSend.PerformClick()
            End Select
        End Sub

        Private Sub Messenger_Load(sender As Object, e As System.EventArgs) Handles Me.Load
            Objects.Classes.Universal.Variables.formMessenger = True

            InitializeSender()
            InitializeReceiver()

            Me.txtMessage.Text = ""
            Me.txtMessage.Focus()
        End Sub

        Private Sub btnSend_Click(sender As System.Object, e As System.EventArgs)
            txtMessage.Text = txtMessage.Text.Trim()

            Dim toSend As String =
                "(" +
                DateTime.Now.ToString("HH:mm") +
                ")" +
                Objects.Classes.Universal.Variables.Username + " > " + txtMessage.Text
            Dim data() As Byte = Encoding.ASCII.GetBytes(toSend)
            sendingClient.Send(data, data.Length)
            Me.txtMessage.Text = ""
            Me.txtMessage.Focus()
        End Sub

        Private Sub MessageReceived(ByRef message As String)
            txtDisplay.Text += message + vbNewLine
        End Sub

        Private Sub InitializeSender()
            sendingClient = New UdpClient(broadcastAddress, port)
            sendingClient.EnableBroadcast = True
        End Sub

        Private Sub InitializeReceiver()
            receivingClient = New UdpClient(port)

            Dim start As ThreadStart = New ThreadStart(AddressOf Receiver)
            receivingThread = New Thread(start)
            receivingThread.IsBackground = True
            receivingThread.Start()
        End Sub

        Private Sub Receiver()
            Dim endPoint As IPEndPoint = New IPEndPoint(IPAddress.Any, port)
            Dim messageDelegate As AddMessage = AddressOf MessageReceived

            While (True)
                Dim data() As Byte
                data = receivingClient.Receive(endPoint)
                Dim message As String = Encoding.ASCII.GetString(data)
                Invoke(messageDelegate, message)
            End While
        End Sub

    End Class
End Namespace