.NET [C#/VB] Simple instance merger class

Code
Imports System.Threading

Imports Microsoft.Win32

Imports System.Net.Sockets

Imports System.Net

Imports System.Reflection

Imports System.IO



''' <summary>

''' Application instance merger

''' Made by BahNahNah

''' uid=2388291

''' 

''' Ported to VB by Tedd

''' </summary>



Public Class SingleInstance

    Public Delegate Sub MergeInstanceCallback(ByVal path As String, ByVal args As String())



    Private applicationMutex As Mutex = Nothing

    Private InstanceKey As String

    Private PortSave As RegistryKey = Nothing

    Private InstanceSocket As Socket = Nothing

    Private SocketBuffer As Byte()

    Private SenderEndpoint As EndPoint = New IPEndPoint(IPAddress.Loopback, 0)

    Private MergeInstance As MergeInstanceCallback



    Public Sub Create(ByVal callback As MergeInstanceCallback)

        Create(callback, 1048576)

    End Sub

    Public Sub Create(ByVal callback As MergeInstanceCallback, ByVal bufferSize As Integer)

        If callback = Nothing Then Return



        MergeInstance = callback



        InstanceKey = Assembly.GetEntryAssembly().GetType().GUID.ToString()

        PortSave = Registry.CurrentUser.OpenSubKey("AppEvents\Instances", True)



        If PortSave Is Nothing Then PortSave = Registry.CurrentUser.CreateSubKey("AppEvents\Instances")



        If InstanceKey = Nothing Then Throw New Exception("Invalid InstanceKey")



        ReDim SocketBuffer(bufferSize)



        Dim instancePort As Integer = GetCurrentInstancePort()



        If instancePort = 0 Then

            CreateNewInstance()

        Else

            MergeInstances(instancePort)

        End If

    End Sub

    Private Sub CreateNewInstance()

        If Not applicationMutex Is Nothing Then applicationMutex.ReleaseMutex()



        applicationMutex = New Mutex(True, InstanceKey)



        InstanceSocket = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)

        InstanceSocket.Bind(SenderEndpoint)

        PortSave.SetValue(InstanceKey, DirectCast(InstanceSocket.LocalEndPoint, IPEndPoint).Port)

        InstanceSocket.BeginReceiveFrom(SocketBuffer, 0, SocketBuffer.Length, SocketFlags.None, SenderEndpoint, AddressOf DataReceived, Nothing)

    End Sub

    Private Sub MergeInstances(ByVal port As Integer)

        InstanceSocket = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)



        Dim args As String() = Environment.GetCommandLineArgs()



        Using ms As MemoryStream = New MemoryStream()

            Using bw As BinaryWriter = New BinaryWriter(ms)

                bw.Write(args.Length)

                For i = 0 To args.Length - 1

                    bw.Write(args(i))

                Next

                InstanceSocket.SendTo(ms.ToArray, New IPEndPoint(IPAddress.Loopback, port))

            End Using

        End Using

        Environment.Exit(0)

    End Sub

    Private Function GetCurrentInstancePort() As Integer

        Try

            applicationMutex = Mutex.OpenExisting(InstanceKey)

            If PortSave Is Nothing Then Return 0

            Return DirectCast(PortSave.GetValue(InstanceKey, 0), Integer)

        Catch ex As Exception

            Return 0

        End Try

    End Function

    Private Sub DataReceived(ByVal AR As IAsyncResult)

        Dim bytesRead As Integer = InstanceSocket.EndReceive(AR)



        If bytesRead = 0 Then

            InstanceSocket.BeginReceiveFrom(SocketBuffer, 0, SocketBuffer.Length, SocketFlags.None, SenderEndpoint, AddressOf DataReceived, Nothing)

            Return

        End If



        Dim data(bytesRead) As Byte

        Buffer.BlockCopy(SocketBuffer, 0, data, 0, data.Length)



        Dim path As String = Nothing

        Dim args() As String = Nothing



        Using ms As MemoryStream = New MemoryStream(data)

            Using br As BinaryReader = New BinaryReader(ms)

                ReDim args(br.ReadInt32() - 1)

                path = br.ReadString()

                For i = 0 To args.Length - 1

                    args(i) = br.ReadString

                Next

            End Using

        End Using

        MergeInstance(path, args)

        InstanceSocket.BeginReceiveFrom(SocketBuffer, 0, SocketBuffer.Length, SocketFlags.None, SenderEndpoint, AddressOf DataReceived, Nothing)

    End Sub

End Class