[RESOLVED] [2008] Can I add a TCPClient Component

[KwongHui]

Well, the code in this thread will just give you a foundation to develop a client/server application. So if you need to be able to communicate with the computers in the "internet cafe" then you have some of the code to help you do so. However that would be just one small piece in building that kind of software. Disabling task managers and all that other non-networking stuff is another story.

Alright, can you tell me which imports class should i use? I have discussed with my friend last night, they suggested UDP for the transport layer. TCP isn't appropriate?

[gooden]

Hi Atheist

I Have a little Question. If i want to send files is better to use a diferent protocol that connects between clients instead of sending The data From Client -> Server -> Other Client

Am i Correct?

[Atheist]

Well..yeah sending entire files between two hosts with the server acting as an intermediate node will put alot of strain on the server. It could also become a bottleneck.
Setting up a separate direct connection between the two hosts for the file transfer is a good idea.

[gooden]

So What i'm Making at this moment is using your TCP IP class to make a private message.

So i will send a comand Like FILESEND|USER|NAMEFILE|SIZE|ETc.... and the in the other side i willl acept the conection Directly from user.

So i don't have to use the server.

=)

Thanks For your help and great job =)

[DrPoncho]

You're a true hero Atheist.

[Drummer]

In your code what is "ConnectedClient"? Have you updated this code? Thanks for your help.

[Atheist]

ConnectedClient is a class that represents a client connected to the server.
I have not yet updated the code, sorry, I just keep forgetting it. As I look at it though...it wouldn't be a major update, but I'd rewrite the sending and receiving parts to utilize a BinaryReader/BinaryWriter instead, and thus remove the need for those pesky "delimiters".

[rydinophor]

ConnectedClient is a class that represents a client connected to the server.
I have not yet updated the code, sorry, I just keep forgetting it. As I look at it though...it wouldn't be a major update, but I'd rewrite the sending and receiving parts to utilize a BinaryReader/BinaryWriter instead, and thus remove the need for those pesky "delimiters".

why not just create a public method for instance:

Public Sep_Char as String = "|:|" ' the |:| is the delimiter
Public End_Char as String = ControlChars.cr

now look how much easier it is:

 
Call SendMessage("packetname" & sep_char & "parse 1" & sep_char & "parse 2" & sep_char & "parse 3" & sep_char & "so forth" & end_char)

there really shouldn't be any need of removing delimiters, makes it easier for me w/ them there .
then you can create a data handling module:

Private Sub messageReceived(ByVal sender As ConnectedClient, ByVal message As String)
Call HandleData(Sender, Message)
end Sub

Sub HandleData(ByVal Index as ConnectedClient, ByVal msg as string)
Dim Casestring as String
Dim Parse() as String
Parse = Split(Msg, SEP_CHAR)
Casestring = Lcase(parse(0))

if casestring = "packetname" then

if parse(1) = "parse 1" then
msgbox("ZOMFG! i got a packet!")
end if

if not parse(2) = "parse 2" then
call sendmessage("packeterror" & end_char)
exit sub
end if

exit sub
end if
end sub

that right there is just a short cut guide for n00bs to Athiests chat program.


On The Other Behalf I would like some help too:


i'm new to all of the .NET framework multiplatform languages, i'm lagging behind w/ the rest of the old timers with VB6, VC++ 6 and etc. and i'm not used to object oriented programming ....sorry....here is my Question:

is there a way i can make an arraylist instead of strings?

i'm aiming to change this code:

Private Sub messageReceived(ByVal sender As ConnectedClient, ByVal message As String)

into something similar to this code:

Private Sub messageReceived(ByVal Sender as Integer, ByVal Message as String)

Thanks in Return,
Rydin


EDIT:
another thing i noticed was that when a client disconnects it fails to remove it and the server bugs too. if there is a fix for this thanks in return =D.

Rydinophor

[Atheist]

why not just create a public method for instance:

Public Sep_Char as String = "|:|" ' the |:| is the delimiter
Public End_Char as String = ControlChars.cr

now look how much easier it is:

 
Call SendMessage("packetname" & sep_char & "parse 1" & sep_char & "parse 2" & sep_char & "parse 3" & sep_char & "so forth" & end_char)

there really shouldn't be any need of removing delimiters, makes it easier for me w/ them there .
then you can create a data handling module:

Private Sub messageReceived(ByVal sender As ConnectedClient, ByVal message As String)
Call HandleData(Sender, Message)
end Sub

Sub HandleData(ByVal Index as ConnectedClient, ByVal msg as string)
Dim Casestring as String
Dim Parse() as String
Parse = Split(Msg, SEP_CHAR)
Casestring = Lcase(parse(0))

if casestring = "packetname" then

if parse(1) = "parse 1" then
msgbox("ZOMFG! i got a packet!")
end if

if not parse(2) = "parse 2" then
call sendmessage("packeterror" & end_char)
exit sub
end if

exit sub
end if
end sub

that right there is just a short cut guide for n00bs to Athiests chat program.

Well, the thing about using character delimiters in text data is that what happens if the text that is to be sent contains the delimiter naturally? In other words, what if the message you'd like to get across to the receiver contains ControlChars.Cr in itself? The receiver would then treat the single message as two separate messages, split on that ControlChars.Cr occurance.
By not using delimiters the text data can contain anything without any problems on the receiving end. It also makes it easier on the coding, as working with delimiters is a bit more tedious than using the BinaryWriter/BinaryReader approach.

On The Other Behalf I would like some help too:


i'm new to all of the .NET framework multiplatform languages, i'm lagging behind w/ the rest of the old timers with VB6, VC++ 6 and etc. and i'm not used to object oriented programming ....sorry....here is my Question:

is there a way i can make an arraylist instead of strings?

i'm aiming to change this code:

Private Sub messageReceived(ByVal sender As ConnectedClient, ByVal message As String)

into something similar to this code:

Private Sub messageReceived(ByVal Sender as Integer, ByVal Message as String)

Thanks in Return,
Rydin

I'm not following, you'd like to use an ArrayList instead of a String where exactly? The only change I can see in your two lines is that you've changed ConnectedClient to Integer.

EDIT:
another thing i noticed was that when a client disconnects it fails to remove it and the server bugs too. if there is a fix for this thanks in return =D.

Rydinophor

Well...if the connection to the client is closed "abruptly" (client software crashes, cable is unplugged etc.), theres no way of avoiding an exception, so all you can do is to catch it, remove the client from your list of connected clients, and move on.
If however the client disconnects gracefully, you would send a message to the server to let it know that this is the case, and close all connections.

[rydinophor]

I'm not following, you'd like to use an ArrayList instead of a String where exactly? The only change I can see in your two lines is that you've changed ConnectedClient to Integer.

in other words is it possible to make it into an array of integers instead of using a class?

Well...if the connection to the client is closed "abruptly" (client software crashes, cable is unplugged etc.), theres no way of avoiding an exception, so all you can do is to catch it, remove the client from your list of connected clients, and move on.
If however the client disconnects gracefully, you would send a message to the server to let it know that this is the case, and close all connections.

i have that fixed, mans 2nd best friend did that:
"On Error Resume Next"

Well, the thing about using character delimiters in text data is that what happens if the text that is to be sent contains the delimiter naturally? In other words, what if the message you'd like to get across to the receiver contains ControlChars.Cr in itself? The receiver would then treat the single message as two separate messages, split on that ControlChars.Cr occurance.
By not using delimiters the text data can contain anything without any problems on the receiving end. It also makes it easier on the coding, as working with delimiters is a bit more tedious than using the BinaryWriter/BinaryReader approach.

i wasn't born yesterday, for instance from what i showed above this packet:
Call SendMessage("packetname" & sep_char & "parse 1" & sep_char & "parse 2" & end_char)
here is what the full string is based off spliting from teh sep_char delmlimiters
"packetname|:|parse 1|:|parse 2then w/e the controlchars.cr string is

[Atheist]

in other words is it possible to make it into an array of integers instead of using a class?

The class itself is what handles the communication with the client, so the best thing you could do, if you want each client to have a unique index, is to give the class an integer member and a public property for this, and give each client an incremented number as they connect.

i have that fixed, mans 2nd best friend did that:
"On Error Resume Next"

On Error Resume Next is the worst way possible to handle exceptions I'm afraid. It's not so much error handling as it is, in fact, error ignoring.

i wasn't born yesterday, for instance from what i showed above this packet:
Call SendMessage("packetname" & sep_char & "parse 1" & sep_char & "parse 2" & end_char)
here is what the full string is based off spliting from teh sep_char delmlimiters
"packetname|:|parse 1|:|parse 2then w/e the controlchars.cr string is

My apologies if I made it sound as if you where born yesterday, I was just presenting you with my reasons for choosing the "size-prefixed" variation over the "delimited" one.
But still, what if "parse 1" in your example consisted of text that the user has written...and the user has written something consisting of either |:| or ControlChars.Cr. This could lead to unexpected results, and even security problems.
When I say security problems; Take this scenario into consideration...
Perhaps you have it so that when a client sends a message to someone else, it sends the following: MESSAGE|:|MyNickName|:|ReciepentsNickName|:|MyMessage
Now...what if I, as a user of your application, writes a message to someone, but in my actual message I write ControlChars.Cr first, and then MESSAGE|:|SomeOneElsesNickName|:|ReciepentsNickName|:|MyMessage.
What would happen if that was sent? Of course, one could argue that you shouldnt let the user write |:| or ControlChars.Cr in the message in the first place, but why restrict the user to avoid unpexpected behaviour, when a better design in the first place could?

[rydinophor]

The class itself is what handles the communication with the client, so the best thing you could do, if you want each client to have a unique index, is to give the class an integer member and a public property for this, and give each client an incremented number as they connect.

i got that array to work now i need to get it to where i can send data to the specified integer member:

   
Private mIndex As Integer
Sub New(ByVal client As System.Net.Sockets.TcpClient, ByVal parentForm As Form1, ByVal IsIndex As Integer)
        mParentForm = parentForm
        mClient = client
mIndex = IsIndex
        mIndex = Index
        readThread = New System.Threading.Thread(AddressOf doRead)
        readThread.IsBackground = True
        readThread.Start()
    End Sub
    Public Property Index() As Integer
        Get
            Return mIndex
        End Get
        Set(ByVal value As Integer)
            mIndex = Index
        End Set
    End Property

Form1:

    Private Sub doListen()
        Dim incomingClient As System.Net.Sockets.TcpClient
        Do
            For i As Integer = 1 To 10
                incomingClient = listener.AcceptTcpClient 'Accept the incoming connection. This is a blocking method so execution will halt here until someone tries to connect.

                Dim connClient As New ConnectedClient(incomingClient, Me, i)

                'Create a new instance of ConnectedClient (check its constructor to see whats happening now).
                AddHandler connClient.dataReceived, AddressOf Me.messageReceived
                'clients.Add(connClient) 'Adds the connected client to the list of connected clients.
                clients.Add(connClient)
            Next
        Loop
    End Sub

i also have found this and never seen this command before:

Dim index As Integer = clients.IndexOf(client)

what will this do?
have any ideas?

On Error Resume Next is the worst way possible to handle exceptions I'm afraid. It's not so much error handling as it is, in fact, error ignoring.

Fixed Also, I used the Try and Catch Method and found the error.

My apologies if I made it sound as if you where born yesterday, I was just presenting you with my reasons for choosing the "size-prefixed" variation over the "delimited" one.
But still, what if "parse 1" in your example consisted of text that the user has written...and the user has written something consisting of either |:| or ControlChars.Cr. This could lead to unexpected results, and even security problems.
When I say security problems; Take this scenario into consideration...
Perhaps you have it so that when a client sends a message to someone else, it sends the following: MESSAGE|:|MyNickName|:|ReciepentsNickName|:|MyMessage
Now...what if I, as a user of your application, writes a message to someone, but in my actual message I write ControlChars.Cr first, and then MESSAGE|:|SomeOneElsesNickName|:|ReciepentsNickName|:|MyMessage.
What would happen if that was sent? Of course, one could argue that you shouldnt let the user write |:| or ControlChars.Cr in the message in the first place, but why restrict the user to avoid unpexpected behaviour, when a better design in the first place could?

Fixed, Thanks =)


Thanks In Return,
Rydinophor

[Atheist]

i got that array to work now i need to get it to where i can send data to the specified integer member:

   
Private mIndex As Integer
Sub New(ByVal client As System.Net.Sockets.TcpClient, ByVal parentForm As Form1, ByVal IsIndex As Integer)
        mParentForm = parentForm
        mClient = client
mIndex = IsIndex
        mIndex = Index
        readThread = New System.Threading.Thread(AddressOf doRead)
        readThread.IsBackground = True
        readThread.Start()
    End Sub
    Public Property Index() As Integer
        Get
            Return mIndex
        End Get
        Set(ByVal value As Integer)
            mIndex = Index
        End Set
    End Property

Form1:

    Private Sub doListen()
        Dim incomingClient As System.Net.Sockets.TcpClient
        Do
            For i As Integer = 1 To 10
                incomingClient = listener.AcceptTcpClient 'Accept the incoming connection. This is a blocking method so execution will halt here until someone tries to connect.

                Dim connClient As New ConnectedClient(incomingClient, Me, i)

                'Create a new instance of ConnectedClient (check its constructor to see whats happening now).
                AddHandler connClient.dataReceived, AddressOf Me.messageReceived
                'clients.Add(connClient) 'Adds the connected client to the list of connected clients.
                clients.Add(connClient)
            Next
        Loop
    End Sub

i also have found this and never seen this command before:

Dim index As Integer = clients.IndexOf(client)

what will this do?
have any ideas?

That IndexOf call will return the index of the client in the clients collection... I suppose you could actually make use of that index altogether and forget about giving the client itself an extra property, like I said in my last post.

Fixed Also, I used the Try and Catch Method and found the error.

Great

[rydinophor]

That IndexOf call will return the index of the client in the clients collection... I suppose you could actually make use of that index altogether and forget about giving the client itself an extra property, like I said in my last post.

i have that covered thanks . now the only problem is changing it back and i just figure that out too:

 Dim Sender As ConnectedClient = clients.Item(Index)
        Sender.SendMessage(Message)

the only problem is i can't call that sub(in frmserver class) from a module(modtcpserver) can you help me out on this one?

[Atheist]

Do you mean that you can not access the clients object from the module?

[rydinophor]

here let me show you what i'm trying to do and its not working:
in Module modServerTCP:

    Sub SendDataTo(ByVal Index As Integer, ByVal Data As String)
        Call frmServer.SendDataTos(Index, Data)
    End Sub

in Public Class frmServer:

    Sub SendDataTos(ByVal Index As Integer, ByVal Message As String)
        MsgBox("this is what i'm trying to access!")
        Dim Sender As ConnectedClient = clients.Item(Index)
        Sender.SendMessage(Message)
End Sub

both of these are in the server.

[Atheist]

You cant access it at all? I think it should be public by default but try adding the Public modifier infront of Sub.

[rydinophor]

nope still didn't work i added public in front of Sub SendDataTos(ByVal Index As Integer, ByVal Message As String)

[Atheist]

In what way can you not access it? I am under the impression that frmServer is the name of your class, and that you are specifying 'frmServer' because you're using the forms default instance. If this is not the case you'll have some more problems.
But lets start with the question; In what way can you not access it? Does it not appear in the intellisense? Do you get an error when trying to call it?

[rydinophor]

nvm i got it something was messing up the packets from behind the calls.
Thanks Again,
Rydinophor

[rydinophor]

sorry for the double post, but i really don't like threaded sockets, can you show an example of Async Sockets? i get this error when coding and the try and catch doesn't even work on it:

The Undo operation encountered a context that is different from what was applied in the corresponding Set operation. The possible cause is that a context was Set on the thread and not reverted(undone).

Thanks In Return,
Rydinophor

[Atheist]

I can't give you an example right now as I'm at work; but show me what you've got and we could work from that.

[rydinophor]

sorry about a no reply for 2 days my mind was on work and offset to java, i used a few async tuts and managed to get it too work, the only prob is when my client disconnects the server absolutely rejects all client requests

[jizzmasterflex]

    Public Sub Senddata(ByVal msg As String)
        Dim sw As New IO.StreamWriter(frmMain.client.GetStream)
        Try
            sw.Write(msg)
            sw.Flush()
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
    End Sub

This senddata sub works fine from frmMain, but I have all my functions and subs inside of a module. I tried creating the sub above so I could put this function inside my module as well, but I keep getting the following error:

"Object reference not set to an instance of an object"

I cannot for the life of me figure out what I am missing. Can anyone share some brain food?

Thank you for your time.

[jizzmasterflex]

sorry for the double post, but i really don't like threaded sockets, can you show an example of Async Sockets? i get this error when coding and the try and catch doesn't even work on it:

The Undo operation encountered a context that is different from what was applied in the corresponding Set operation. The possible cause is that a context was Set on the thread and not reverted(undone).

Thanks In Return,
Rydinophor

First off sorry for the double post. I also am running into this problem. Would you mind saying how you fixed it?

thanks!

[rydinophor]

I never managed to fix the issue, instead i switched to asynchronous sockets.

I don't know where to start but I've been looking for something like this for months, I took a look at atheists simple chat program with threaded sockets but no sooner then i tryed i found out that Asynchronous Sockets run 20x faster then Threaded sockets, So I would like to contribute to the community as well and post my Chat Example Program In which you can send data back and forth to specific clients:

TCP Client Side:
In Form1:

'
'C# Network Programming 
'by Richard Blum
'
'Publisher: Sybex 
'ISBN: 0782141765
'


Imports System
Imports System.Drawing
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.Windows.Forms


Public Class AsyncTcpClient
    Inherits Form
    Private newText As TextBox
    Private conStatus As TextBox
    Private results As ListBox
    Private client As Socket
    Private data As Byte() = New Byte(1023) {}
    Private sizes As Integer = 1024

    Public Sub New()
        Text = "Asynchronous TCP Client"
        Size = New Size(400, 380)

        Dim label1 As New Label()
        label1.Parent = Me
        label1.Text = "Enter text string:"
        label1.AutoSize = True
        label1.Location = New Point(10, 30)

        newText = New TextBox()
        newText.Parent = Me
        newText.Size = New Size(200, 2 * Font.Height)
        newText.Location = New Point(10, 55)

        results = New ListBox()
        results.Parent = Me
        results.Location = New Point(10, 85)
        results.Size = New Size(360, 18 * Font.Height)

        Dim label2 As New Label()
        label2.Parent = Me
        label2.Text = "Connection Status:"
        label2.AutoSize = True
        label2.Location = New Point(10, 330)

        conStatus = New TextBox()
        conStatus.Parent = Me
        SetConnectionLabelText("Disconnected")
        conStatus.Size = New Size(200, 2 * Font.Height)
        conStatus.Location = New Point(110, 325)

        Dim sendit As New Button()
        sendit.Parent = Me
        sendit.Text = "Send"
        sendit.Location = New Point(220, 52)
        sendit.Size = New Size(5 * Font.Height, 2 * Font.Height)
        AddHandler sendit.Click, AddressOf ButtonSendOnClick

        Dim connect As New Button()
        connect.Parent = Me
        connect.Text = "Connect"
        connect.Location = New Point(295, 20)
        connect.Size = New Size(6 * Font.Height, 2 * Font.Height)
        AddHandler connect.Click, AddressOf ButtonConnectOnClick

        Dim discon As New Button()
        discon.Parent = Me
        discon.Text = "Disconnect"
        discon.Location = New Point(295, 52)
        discon.Size = New Size(6 * Font.Height, 2 * Font.Height)
        AddHandler discon.Click, AddressOf ButtonDisconOnClick
    End Sub

    Private Sub ButtonConnectOnClick(ByVal obj As Object, ByVal ea As EventArgs)
        SetConnectionLabelText("Connecting...")
        Dim newsock As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
        Dim iep As New IPEndPoint(IPAddress.Parse("127.0.0.1"), 9050)
        newsock.BeginConnect(iep, New AsyncCallback(AddressOf Connected), newsock)
    End Sub

    Private Sub ButtonSendOnClick(ByVal obj As Object, ByVal ea As EventArgs)
        Dim message As Byte() = Encoding.ASCII.GetBytes(newText.Text)
        newText.Clear()
        client.BeginSend(message, 0, message.Length, SocketFlags.None, New AsyncCallback(AddressOf SendData), client)
    End Sub

    Private Sub ButtonDisconOnClick(ByVal obj As Object, ByVal ea As EventArgs)
        client.Close()
        SetConnectionLabelText("Disconnected")
    End Sub

    Private Sub Connected(ByVal iar As IAsyncResult)
        client = DirectCast(iar.AsyncState, Socket)
        Try
            client.EndConnect(iar)
            SetConnectionLabelText("Connected to: " & client.RemoteEndPoint.ToString())
            client.BeginReceive(data, 0, sizes, SocketFlags.None, New AsyncCallback(AddressOf ReceiveData), client)
        Catch generatedExceptionName As SocketException
            SetConnectionLabelText("Error connecting")
        End Try
    End Sub
    Private Delegate Sub StringDelegate(ByVal text As String)

    Private Sub SetConnectionLabelText(ByVal text As String)
        If conStatus.InvokeRequired Then
            Me.Invoke(New StringDelegate(AddressOf SetConnectionLabelText), text)
        Else
            conStatus.Text = text
        End If
    End Sub
    Private Sub ReceiveData(ByVal iar As IAsyncResult)
        Dim remote As Socket = DirectCast(iar.AsyncState, Socket)
        Dim recv As Integer = remote.EndReceive(iar)
        Dim stringData As String = Encoding.ASCII.GetString(data, 0, recv)
        SetText(stringData & vbCrLf)
    End Sub
    Private Delegate Sub StringDel(ByVal text As String)
    Private Sub SetText(ByVal text As String)
        If results.InvokeRequired Then
            Me.Invoke(New StringDel(AddressOf SetText), text)
        Else
            results.Text = text
        End If
    End Sub

    Private Sub SendData(ByVal iar As IAsyncResult)
        Dim remote As Socket = DirectCast(iar.AsyncState, Socket)
        Dim sent As Integer = remote.EndSend(iar)
        remote.BeginReceive(data, 0, sizes, SocketFlags.None, New AsyncCallback(AddressOf ReceiveData), remote)
    End Sub

    Public Shared Sub Main()
        Application.Run(New AsyncTcpClient())
    End Sub
End Class

Server Side:
In Form1:

Imports System.Net.Sockets
Imports System.Net
Imports System.Text
Public Class Form1
    Public SEP_CHAR As String = "|"
    Private data As Byte() = New Byte(1023) {}
    Private sizes As Integer = 1024
    Private server As Socket
    Dim ClientList As New List(Of Socket)
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        server = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
        Dim End_Point As New IPEndPoint(IPAddress.Any, 9050)
        server.Bind(End_Point)
        server.Listen(5)
        server.BeginAccept(New AsyncCallback(AddressOf AcceptConn), server)
    End Sub
    Private Sub AcceptConn(ByVal iar As IAsyncResult)
        Dim oldserver As Socket = DirectCast(iar.AsyncState, Socket)
        ' Client = DirectCast(iar.AsyncState, Socket)
        Dim client As Socket = oldserver.EndAccept(iar) '
        ClientList.Add(client)
        SetConnectionLabelText("Connected to: ") '& Client.RemoteEndPoint.ToString)
        Dim stringData As String = "Welcome to my server"
        Dim message1 As Byte() = Encoding.ASCII.GetBytes(stringData)
        ClientList(ClientList.IndexOf(client)).BeginSend(message1, 0, message1.Length, SocketFlags.None, New AsyncCallback(AddressOf SendData), ClientList.Item(ClientList.IndexOf(client)))
    End Sub
    Private Delegate Sub StringDelegate(ByVal text As String)

    Private Sub SetConnectionLabelText(ByVal text As String)
        If TextBox1.InvokeRequired Then
            Me.Invoke(New StringDelegate(AddressOf SetConnectionLabelText), TextBox1.Text & text & vbCrLf)
        Else
            TextBox1.Text = text
        End If
    End Sub
    Private Sub SendData(ByVal iar As IAsyncResult)
        'w/e that was was really strange it feels like 2012 december 21 right now lol
        Dim sent As Integer = ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))).EndSend(iar) 'hmm
        ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))).BeginReceive(data, 0, sizes, SocketFlags.None, New AsyncCallback(AddressOf ReceiveData), ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))))
    End Sub

    Private Sub ReceiveData(ByVal iar As IAsyncResult)
        On Error Resume Next
        Dim recv As Integer
        recv = ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))).EndReceive(iar)
        If recv = 0 Then
            ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))).Close()
            SetConnectionLabelText("Waiting for client...")
            server.BeginAccept(New AsyncCallback(AddressOf AcceptConn), server)
            Exit Sub
        End If
        Dim receivedData As String = Encoding.ASCII.GetString(data, 0, recv)
        ' Call SetConnectionLabelText(TextBox1.Text & receivedData & vbNewLine)
        Call HandleData(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket)), receivedData)
        Dim message2 As Byte() = Encoding.ASCII.GetBytes(receivedData)
        ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))).BeginSend(message2, 0, message2.Length, SocketFlags.None, New AsyncCallback(AddressOf SendData), ClientList.Item(ClientList.IndexOf(DirectCast(iar.AsyncState, Socket))))
    End Sub
    Sub HandleData(ByVal Index As Integer, ByVal Data As String)
        Dim CaseString() As String = Data.Split("|"c) 'Split the message on each | and place in the string array.
        Dim Parse() As String = Data.Split("|"c)
        Select Case CaseString(0)
            Case "bob"
                If Parse(1) = "yes" Then
                    SetConnectionLabelText("ZOMFG! The Case Worked!")
                    Exit Sub
                End If
        End Select
    End Sub
End Class

Credit Goes To Athiest For A Few Snippets and http://www.java2s.com/Code/CSharp/Ne...cTcpServer.htm

[rydinophor]

Sorry For The Double Post but is there anyway of accessing the forms controls from another module? I tried adding some text to textbox1 in form1 from modtcpinit and its not working very well, any suggestions?

Thanks In Return,
Rydinophor

[fredfish]

hey Atheist, thanks for the great example code. I've started to use it and have noticed that when i disconnect, and send a "DISCONNECT" message, the client gets removed from the list but from that point onwards, the program starts taking up most of my CPU cycles - doRead is looping. Is there anything I can do to stop this?

thanks in advance

[Raziiq]

This is my version of the code but its not working for me

Server

Imports System.Net.Sockets
Imports System.Net
Imports System.IO

Public Class Form1
    Dim myListener As TcpListener
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        myListener = New TcpListener(Net.IPAddress.Any, 8000)
        myListener.Start()
        Button1.Enabled = False
        lblConnect.Text = "Connected to Port No 8000"
        DoListen()
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub DoListen()

        'This is the sub that does all the actual "listening". Its an endless loop that calls the AcceptTcpClient method over and over.

        'If there is no connecting TcpClient, it will raise an exception but we will ignore this by catching it in a try statement and doing nothing with it.

        'On the other hand, If a client has connected, it proceeds to the next line and a streamreader reads the incoming stream and shows it in a messagebox.
        Dim sr As IO.StreamReader

        Do

            Try
                Dim client As Net.Sockets.TcpClient = myListener.AcceptTcpClient

                sr = New IO.StreamReader(client.GetStream)
                MessageBox.Show(sr.ReadToEnd)

                sr.Close()

            Catch

            End Try
        Loop

    End Sub

    Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click
        End
    End Sub
End Class

Client

Imports System.IO
Imports System.Net
Imports System.Net.Sockets

Public Class Form1
    Private client As System.Net.Sockets.TcpClient
    Private Const BYTES_TO_READ As Integer = 255
    Private readBuffer(BYTES_TO_READ) As Byte

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub messageReceived(ByVal message As String)
        MessageBox.Show(message)
    End Sub



    Private Sub SendMessage(ByVal msg As String)
        Dim sw As IO.StreamWriter
        Try
            sw = New IO.StreamWriter(client.GetStream)
            sw.Write(msg)
            sw.Flush()
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        client = New System.Net.Sockets.TcpClient("localhost", 8000)
        client.GetStream.BeginRead(readBuffer, 0, BYTES_TO_READ, AddressOf doRead, Nothing)
    End Sub

    Private Sub doRead(ByVal ar As System.IAsyncResult)
        Dim totalRead As Integer
        Try
            totalRead = client.GetStream.EndRead(ar) 'Ends the reading and returns the number of bytes read.
        Catch ex As Exception
            'The underlying socket have probably been closed OR an error has occured whilst trying to access it, either way, this is where you should remove close all eventuall connections
            'to this client and remove it from the list of connected clients.
        End Try

        If totalRead > 0 Then
            'the readBuffer array will contain everything read from the client.
            Dim receivedString As String = System.Text.Encoding.UTF8.GetString(readBuffer, 0, totalRead)
            messageReceived(receivedString)
        End If

        Try
            client.GetStream.BeginRead(readBuffer, 0, BYTES_TO_READ, AddressOf doRead, Nothing) 'Begin the reading again.
        Catch ex As Exception
            'The underlying socket have probably been closed OR an error has occured whilst trying to access it, either way, this is where you should remove close all eventuall connections
            'to this client and remove it from the list of connected clients.
        End Try
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        SendMessage("Hi there")
    End Sub
End Class

Can anybody help me out with this?

[adamj12b]

What is the error you are getting?

-Adam

[korae]

what if you want to stop listener? I mean if the user wants to change username or port?

This is where you start to listen from clients:

listener = New TcpListener(IPAddress.Any, txtPort.Text)
listener.Start() 'Start listening.
listenThread = New Thread(AddressOf DoListen)
listenThread.IsBackground = True
listenThread.Start()

And here's the DoListen

Private Sub DoListen()
Dim incomingClient As System.Net.Sockets.TcpClient
Do
incomingClient = listener.AcceptTcpClient
Dim connClient As New ConnectedClient(incomingClient, Me)
AddHandler connClient.dataReceived, AddressOf Me.MessageReceived
clients.Add(connClient) 'Adds the connected client to the list of connected clients.
Me.MessageReceived
Loop
End Sub

How do you stop listener? I tried doing this but I always get an error:

listener.Stop()
listenThread.Abort()

[korae]

oh I already solved my first question well I have another one:

this code to connects to server:

client = New TcpClient(txtIP.Text, txtPort.Text)
client.GetStream.BeginRead(readBuffer, 0, BYTES_TO_READ, AddressOf DoRead, Nothing)
SendMessage("/CONNECT|" & Label25.Text)

How do I check if the TcpListener is available?

I get this error when I run it without a server

"No connection could be made because the target machine actively refused it 127.0.0.1:43000"

What if the client is running then suddenly the server restarts?

[coolcurrent4u]

In the specific post by me that you linked too, there is only code for the server side. But in the same thread, I've got examples for the client side aswell.
Anyway, I'll create one more example..

Server side:
Form:

Public Class Form1
    Private listener As System.Net.Sockets.TcpListener
    Private listenThread As System.Threading.Thread
 
    Private clients As New List(Of ConnectedClient) 'This list will store all connected clients.
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        listener = New System.Net.Sockets.TcpListener(System.Net.IPAddress.Any, 43001) 'The TcpListener will listen for incoming connections at port 43001
        listener.Start() 'Start listening.
        listenThread = New System.Threading.Thread(AddressOf doListen) 'This thread will run the doListen method
        listenThread.IsBackground = True 'Since we dont want this thread to keep on running after the application closes, we set isBackground to true.
        listenThread.Start() 'Start executing doListen on the worker thread.
    End Sub
 
    Private Sub doListen()
        Dim incomingClient As System.Net.Sockets.TcpClient
        Do
            incomingClient = listener.AcceptTcpClient 'Accept the incoming connection. This is a blocking method so execution will halt here until someone tries to connect.
            Dim connClient As New ConnectedClient(incomingClient, Me) 'Create a new instance of ConnectedClient (check its constructor to see whats happening now).
            AddHandler connClient.dataReceived, AddressOf Me.messageReceived
            clients.Add(connClient) 'Adds the connected client to the list of connected clients.
 
        Loop
    End Sub
 
    Public Sub removeClient(ByVal client As ConnectedClient)
        If clients.Contains(client) Then
            clients.Remove(client)
        End If
    End Sub
 
    Private Sub messageReceived(ByVal sender As ConnectedClient, ByVal message As String)
        'A message has been received from one of the clients.
        'To determine who its from, use the sender object.
        'sender.SendMessage can be used to reply to the sender.
 
        Dim data() As String = message.Split("|"c) 'Split the message on each | and place in the string array.
        Select Case data(0)
            Case "CONNECT"
                'We use GetClientByName to make sure no one else is using this username.
                'It will return Nothing if the username is free.
                'Since the client sent the message in this format: CONNECT|UserName, the username will be in the array on index 1.
                If GetClientByName(data(1)) Is Nothing Then
                    'The username is not taken, we can safely assign it to the sender.
                    sender.Username = data(1)
                End If
            Case "DISCONNECT"
                removeClient(sender)
        End Select
 
    End Sub
 
    Private Function GetClientByName(ByVal name As String) As ConnectedClient
        For Each cc As ConnectedClient In clients
            If cc.Username = name Then
                Return cc 'client found, return it.
            End If
        Next
        'If we've reached this part of the method, there is no client by that name
        Return Nothing
    End Function
End Class

ConnectedClient class:

Public Class ConnectedClient
    Private mClient As System.Net.Sockets.TcpClient
 
    Private mUsername As String
    Private mParentForm As Form1
    Private readThread As System.Threading.Thread
    Private Const MESSAGE_DELIMITER As Char = ControlChars.Cr
 
    Public Event dataReceived(ByVal sender As ConnectedClient, ByVal message As String)
 
    Sub New(ByVal client As System.Net.Sockets.TcpClient, ByVal parentForm As Form1)
        mParentForm = parentForm
        mClient = client
 
        readThread = New System.Threading.Thread(AddressOf doRead)
        readThread.IsBackground = True
        readThread.Start()
    End Sub
 
    Public Property Username() As String
        Get
            Return mUsername
        End Get
        Set(ByVal value As String)
            mUsername = value
        End Set
    End Property
 
    Private Sub doRead()
        Const BYTES_TO_READ As Integer = 255
        Dim readBuffer(BYTES_TO_READ) As Byte
        Dim bytesRead As Integer
        Dim sBuilder As New System.Text.StringBuilder
        Do
            bytesRead = mClient.GetStream.Read(readBuffer, 0, BYTES_TO_READ)
            If (bytesRead > 0) Then
                Dim message As String = System.Text.Encoding.UTF8.GetString(readBuffer, 0, bytesRead)
                If (message.IndexOf(MESSAGE_DELIMITER) > -1) Then
 
                    Dim subMessages() As String = message.Split(MESSAGE_DELIMITER)
 
                    'The first element in the subMessages string array must be the last part of the current message.
                    'So we append it to the StringBuilder and raise the dataReceived event
                    sBuilder.Append(subMessages(0))
                    RaiseEvent dataReceived(Me, sBuilder.ToString)
                    sBuilder = New System.Text.StringBuilder
 
                    'If there are only 2 elements in the array, we know that the second one is an incomplete message,
                    'though if there are more then two then every element inbetween the first and the last are complete messages:
                    If subMessages.Length = 2 Then
                        sBuilder.Append(subMessages(1))
                    Else
                        For i As Integer = 1 To subMessages.GetUpperBound(0) - 1
                            RaiseEvent dataReceived(Me, subMessages(i))
                        Next
                        sBuilder.Append(subMessages(subMessages.GetUpperBound(0)))
                    End If
                Else
 
                    'MESSAGE_DELIMITER was not found in the message, so we just append everything to the stringbuilder.
                    sBuilder.Append(message)
                End If
            End If
        Loop
    End Sub
 
    Public Sub SendMessage(ByVal msg As String)
        Dim sw As IO.StreamWriter
        Try
            SyncLock mClient.GetStream
                sw = New IO.StreamWriter(mClient.GetStream) 'Create a new streamwriter that will be writing directly to the networkstream.
                sw.Write(msg)
                sw.Flush()
            End SyncLock
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
        'As opposed to writing to a file, we DONT call close on the streamwriter, since we dont want to close the stream.
    End Sub
 
End Class

Client Side:
Form:

Public Class Form1
    Private client As System.Net.Sockets.TcpClient
 
    Private Const BYTES_TO_READ As Integer = 255
    Private readBuffer(BYTES_TO_READ) As Byte
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        client = New System.Net.Sockets.TcpClient("localhost", 43001)
        client.GetStream.BeginRead(readBuffer, 0, BYTES_TO_READ, AddressOf doRead, Nothing)
    End Sub
 
    Private Sub doRead(ByVal ar As System.IAsyncResult)
        Dim totalRead As Integer
        Try
            totalRead = client.GetStream.EndRead(ar) 'Ends the reading and returns the number of bytes read.
        Catch ex As Exception
            'The underlying socket have probably been closed OR an error has occured whilst trying to access it, either way, this is where you should remove close all eventuall connections
            'to this client and remove it from the list of connected clients.
        End Try
 
            If totalRead > 0 Then
                'the readBuffer array will contain everything read from the client.
                Dim receivedString As String = System.Text.Encoding.UTF8.GetString(readBuffer, 0, totalRead)
                messageReceived(receivedString)
            End If
 
            Try
                client.GetStream.BeginRead(readBuffer, 0, BYTES_TO_READ, AddressOf doRead, Nothing) 'Begin the reading again.
            Catch ex As Exception
                'The underlying socket have probably been closed OR an error has occured whilst trying to access it, either way, this is where you should remove close all eventuall connections
                'to this client and remove it from the list of connected clients.
            End Try
    End Sub
 
    Private Sub messageReceived(ByVal message As String)
        MessageBox.Show(message)
    End Sub
 
 
 
    Private Sub SendMessage(ByVal msg As String)
        Dim sw As IO.StreamWriter
        Try
            sw = New IO.StreamWriter(client.GetStream)
            sw.Write(msg)
            sw.Flush()
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
    End Sub
End Class

You need to add more exception handling and possibly some SyncLocks upon accessing the different Streams. There are also some important things that I've left out, such as removing a client from the list of connected client upon disconnection.
I've tried to put some comments in the code but dont hesitate to look the different methods/classes up on MSDN.

Edit: I intend to update this example some day soon.

Hello,

Am new to socket programming, and i like your example. but i want to rap this up in a class, so that i can share it among my app that needs socket functionality.

can you help me please?

[stefanACM]

Hey Atheist can you explain this code a little??? I send you one message if you can just answer me i need help urgently
Thanks

[blakrose777]

Hello all, I am also in net programming and this example has proven very useful. A quick question though. How can the value of the Message_Delimiter be changed? Thanks.

[bmaster]

oddly enough though if I make the thread sleep for 1 ms during the read loop.... things work properly in both the IDE and the compiled exe.

Sorry for replying to this really old posts, but the past week I've been trying to use this code myself, and had the same problem as you. It took me a couple of days to find the problem...

In the constructor of the connectedClient class, the thread is started to start listening. However, in the doListen function, the event-handlers are added AFTER the line "Dim connClient As New ConnectedClient(incomingClient)". This means that it is possible that data comes in before the eventhandlers are added, meaning that the data is lost. I fixed the connectedClient class like this:

    Sub New(ByVal client As System.Net.Sockets.TcpClient)
        mClient = client
    End Sub

    Public Sub StartReading()
        readThread = New System.Threading.Thread(AddressOf doRead)
        readThread.IsBackground = False
        readThread.Start()
    End Sub

[bmaster]

    Sub New(ByVal client As System.Net.Sockets.TcpClient)
        mClient = client
    End Sub

    Public Sub StartReading()
        readThread = New System.Threading.Thread(AddressOf doRead)
        readThread.IsBackground = False
        readThread.Start()
    End Sub

Oh, and then of course after creating the new client, and doing the AddHandler-stuff, you call StartReading, otherwise not much data will be read

[blackone]

Hi!
I have 1 question.

how must look send message from client so it would be recognized by server on doread sub and send it to messagerecived sub?

I try this on client:

sw.Write("CONNECT|" & txtNick.Text)
sw.Write("DISCONNECT|" & txtNick.Text)
sw.Write("MESSAGE|" & txtNick.Text & "|" & txtMessage.Text)

but every time can't pass on message_delimiter

If (message.IndexOf(MESSAGE_DELIMITER) > -1) Then..

This is code od doRead()

Private Const MESSAGE_DELIMITER As Char = ControlChars.Cr

 Private Sub doRead()

        Const BYTES_TO_READ As Integer = 255
        Dim readBuffer(BYTES_TO_READ) As Byte
        Dim bytesRead As Integer
        Dim sBuilder As New System.Text.StringBuilder
        Do
            bytesRead = mClient.GetStream.Read(readBuffer, 0, BYTES_TO_READ)
            If (bytesRead > 0) Then
                Dim message As String = System.Text.Encoding.UTF8.GetString(readBuffer, 0, bytesRead)
                If (message.IndexOf(MESSAGE_DELIMITER) > -1) Then


                    Dim subMessages() As String = message.Split(MESSAGE_DELIMITER)

                    'The first element in the subMessages string array must be the last part of the current message.
                    'So we append it to the StringBuilder and raise the dataReceived event
                    sBuilder.Append(subMessages(0))
                    RaiseEvent dataReceived(Me, sBuilder.ToString)
                    sBuilder = New System.Text.StringBuilder


                    'If there are only 2 elements in the array, we know that the second one is an incomplete message,
                    'though if there are more then two then every element inbetween the first and the last are complete messages:
                    If subMessages.Length = 2 Then
                        sBuilder.Append(subMessages(1))
                    Else
                        For i As Integer = 1 To subMessages.GetUpperBound(0) - 1
                            RaiseEvent dataReceived(Me, subMessages(i))
                        Next
                        sBuilder.Append(subMessages(subMessages.GetUpperBound(0)))
                    End If
                Else

                    'MESSAGE_DELIMITER was not found in the message, so we just append everything to the stringbuilder.
                    sBuilder.Append(message)
                End If
            End If
        Loop
    End Sub

How can I fix my problem?
Please help =)

[blackone]

I fix the error and now it's working perfect but now I have another problem

when I send form server 2 message in same time client recived message in one line like this:
NEW|BlackOneUSERLIST|nickname1USERLIST|nickname2

but i need to recived message look like this
1. message NEW|BlackOne
2. message USERLIST|nickname1
3. message USERLIST|nickname2



Case "CONNECT"
If GetClientByName(data(1)) Is Nothing Then
sender.Username = data(1)
sender.SendMessage("WELCOME|" & txtServerName.Text & "|" & txtMessageOfDay.Text & ControlChars.Cr)
Setmessage("New user connected to server: " & data(1))
adduser(data(1))
Dim i As Integer

For Each cc As ConnectedClient In clients
cc.SendMessage("NEW|" & sender.Username & ControlChars.Cr)
Next

For i = 0 To lbUserlist.Items.Count - 1
sender.SendMessage("USERLIST|" & lbUserlist.Items(i) & ControlChars.Cr)
Next

Else

End If



how can I fix that error?

Sorry for bed English

[trashman2012]

hey guys, i'm trying to make a client send messages to another client, but i fail every time,and when i do manage, my privatemessage form freezez, or client2 can't send back messages to client1, pls help