Wait unit an event is raised

Question

I'm trying to make a code that waits until an event is raised. I used the answer in this answer page for Tcp communication. The event PacketReceived will be raised when a packet is received.

Private Sub FooBar()
    'Send some Tcp Message here`

    'Wait until a reply is received here

    'Execute some code when reply is received

End Sub

This is code Sends the filename and what's the file for. It lacks of file existence checking

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        Dim t = New Thread(AddressOf SendFile)
        Dim f = New FileAndData
        f.FileList = SlideShowItems
        f.FileType = "tempSlideShowImage"
        t.Start(f)
    End Sub

    Private Sub SendFile(obj As Object)
        Dim fD = CType(obj, FileAndData)
        For Each item In fD.FileList.Items
            Dim fileIn As New FileStream(item, FileMode.Open)
            Const chunkSize = 10485760

            Dim messageFileNamePkt As New TcpMessagePacket(Encoding.Default.GetBytes(Path.GetFileName(item)), TcpMessagePacket.PacketHeader.Filename)
            messageFileNamePkt.Send(_etcClient.Client) 'Send file name

            Dim messageFiletype As New TcpMessagePacket(Encoding.Default.GetBytes(fD.FileType), TcpMessagePacket.PacketHeader.Filetype)
            messageFiletype.Send(_etcClient.Client) 'Send file type

            'Wait here for reply if for file existence

            While fileIn.Position < fileIn.Length
                Dim bytes(chunkSize) As Byte
                If fileIn.Length - fileIn.Position < bytes.Length Then
                    ReDim bytes(fileIn.Length - fileIn.Position - 1)
                End If
                fileIn.Read(bytes, 0, bytes.Length)

                Dim messageFilePkt As New TcpMessagePacket(bytes, TcpMessagePacket.PacketHeader.FileData)
                messageFilePkt.Send(_etcClient.Client) 'Send file chunks

            End While

            fileIn.Close()
            Dim messageFileEnd As New TcpMessagePacket(Encoding.Default.GetBytes(""), TcpMessagePacket.PacketHeader.TransferComplete)
            messageFileEnd.Send(_etcClient.Client) 'Send transfer complete

        Next
    End Sub

Public Class FileAndData
    Public FileList As ListBox
    Public FileType As String
End Class

And this is the handler for the reply

    Private Sub Client_PacketReceived(sender As Object, e As ExtendedTcpClient.PacketReceivedEventArgs) Handles _etcClient.PacketReceived
    End Sub

Hi there! It's a nice implementation of my code you have here, however there are two things I'd like to point out that could make it a bit more efficient: **1)** A chunk size of 10485760 bytes (10 MB) is _very_ much to put into the network buffer for each send and will most likely slow things down greatly. -- From conducting my own tests I have found that the ideal buffer size is 8192-32768 (8-32 KB) - even over LAN. Everything above and below those values caused the sending to go much slower. — Visual Vincent, Nov 19 '16 at 10:45
(Had to split this into two comments): **2)** When sending packets with no data, instead of `Encoding.Default.GetBytes("")` you could just do: `New Byte() {}` to create an empty byte array. The execution speed difference between the two will likely only be a few hundred microseconds up to a millisecond, but it's still an improvement that removes unnecessary processing. — Visual Vincent, Nov 19 '16 at 10:49

score 3 · Accepted Answer · answered Nov 19 '16 at 08:58

Use ManualResetEvent. Ex.

Imports System.Threading
Module Module1
    Private ReadOnly WaitEvent As New ManualResetEvent(True)
    Sub Main()
        For i = 1 To 100
            WaitEvent.WaitOne() 'This is like a door. It's open because of ManualResetEvent(True)
            If i = 50 Then
                WaitEvent.Reset() 'This closes the door
            End If
            Console.WriteLine(i)
        Next
        Console.Read()
    End Sub
    Private Sub SetTheEventWhenCalled()
        WaitEvent.Set() 'This on the other hand, Opens the door
    End Sub
End Module

Wait unit an event is raised

1 Answers1