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

[perito]

ok.. Im trying to remove the client name from lbClient
I have this code

    Public Sub removeClient(ByVal client As ConnectedClient, ByVal ClientName As String)
        If clients.Contains(client) Then
            clients.Remove(client)
            For x = 0 To lbClients.Items.Count - 1
                If lbClients.Items.Item(x) = ClientName Then lbClients.Items.Remove(lbClients.Items.Item(x))
            Next
        End If
    End Sub

as u see I created ClientName as string in the argument, but I donno how to add it to the declaration in the class

mParentForm.removeClient(Me)

must be changed and I must add something, what is it?

[Atheist]

ok.. Im trying to remove the client name from lbClient
I have this code

    Public Sub removeClient(ByVal client As ConnectedClient, ByVal ClientName As String)
        If clients.Contains(client) Then
            clients.Remove(client)
            For x = 0 To lbClients.Items.Count - 1
                If lbClients.Items.Item(x) = ClientName Then lbClients.Items.Remove(lbClients.Items.Item(x))
            Next
        End If
    End Sub

as u see I created ClientName as string in the argument, but I donno how to add it to the declaration in the class

mParentForm.removeClient(Me)

must be changed and I must add something, what is it?

You can actually get rid of the Clientname argument, sending the client itself is sufficient, because you can then use Client.Username to get its name.

[perito]

hmmm
The code is complete ?

I cant think of anything to add/change? :P
Do you think we should improve more, or is this enough?

The thread is resolved thanks to Atheist )

[Atheist]

hmmm
The code is complete ?

I cant think of anything to add/change? :P
Do you think we should improve more, or is this enough?

The thread is resolved thanks to Atheist )

Good to hear its all working for you now
If everything is working as it should then you shouldnt change it. But if you need to adjust something in the future its very simple. Thats the advantage of learning how to use the System.Net.Socket classes instead of downloading ready-to-use components, its very versatile.

[perito]

ok one more question,
if I want to send small files (jpg lets say) from the server to client or back.
will i have to change all the code? is this a new program? or can I add some things?

[Atheist]

ok one more question,
if I want to send small files (jpg lets say) from the server to client or back.
will i have to change all the code? is this a new program? or can I add some things?

hmm I've never tried to be honest, but it may require you to write to the stream using a System.Io.BinaryWriter instead of a System.IO.StreamWriter. And read from it using a System.IO.BinaryReader. I'll try to whip up some examples of that aswell.

[perito]

k thx

[perito]

I have another question,
if I want to connect to an IRC Channel
is this code useful? or is it a tottally different code? how can I connect to IRC channels?

[^^vampire^^]

Go to mirc.com and look around they have a link to RFC's that detail the IRC client, server and other protocols. The code Atheist has provided for the client is sufficient but there is an enormous amount of coding that will need to be done if you want to correctly make a properly functioning IRC client. Also some of the code will obviously need to be changed to deal with the IRC protocols.

Atheist... I know a while ago we went over this whole tcp/sockets thing and u showed me collecting the clients in Hashtable but now i see you have used a List (Of ConnectedClients) - Which is better to use?

[Atheist]

....Atheist... I know a while ago we went over this whole tcp/sockets thing and u showed me collecting the clients in Hashtable but now i see you have used a List (Of ConnectedClients) - Which is better to use?

A Hashtable is a collection of value/key pairs, meaning that when you add a client to it, you add its key (preferably the clients username) at the same time, so that the client object and the string key is added to the hashtable as a pair. You can then retrieve a client from it by specifying its username.

Dim clientCollection As New HashTable
clientCollection.Add("This is a username", clientObject)

A List(Of T) is simpler, because you can not give the clients a key upon adding them. In the above example I've chosen to give each client a UserName property instead, and create my own GetClientByName function.

You can of course use which one you'd like, but I prefer the List(Of T) way.

[kaisellgren]

How would you list all servers on client side? Also, if you block the connection with firewall the program throws an error on server side once pressing the Listen button.

[Atheist]

How would you list all servers on client side? Also, if you block the connection with firewall the program throws an error on server side once pressing the Listen button.

1. You can not list all servers without having a "master server" to keep track of the servers.
2. Thats why you should place all connection attempts in Try-Catch blocks.

[kaisellgren]

1. You can not list all servers without having a "master server" to keep track of the servers.
2. Thats why you should place all connection attempts in Try-Catch blocks.

So all games like Counter-Strike have their servers oin a global master server? How does this sound:

1) When server is created, the server sends http request to www.master.com/addserver.php?ip=xxxx
2) When client window opens it sends http request to www.master.com/getservers.php and then it lists all IPs.
3) When server closes it sends http request to www.master.com/removeserver.php?ip=xxxx

Sounds good?

[Atheist]

So all games like Counter-Strike have their servers oin a global master server?

Yeah, one or more master servers.

How does this sound:

1) When server is created, the server sends http request to www.master.com/addserver.php?ip=xxxx
2) When client window opens it sends http request to www.master.com/getservers.php and then it lists all IPs.
3) When server closes it sends http request to www.master.com/removeserver.php?ip=xxxx

Sounds good?

Yeah that will work, except for the fact that anyone can use their browser and remove/add servers just to ruin the "system".

[kaisellgren]

This isn't working

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Try
            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.   
        Catch ex As Exception
            Timer1.Enabled = False
            Timer1.Interval = 5000
            Timer1.Enabled = True
            Exit Sub
        End Try
    End Sub

I have the same code in initial button press.

[Atheist]

This isn't working

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Try
            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.   
        Catch ex As Exception
            Timer1.Enabled = False
            Timer1.Interval = 5000
            Timer1.Enabled = True
            Exit Sub
        End Try
    End Sub

I have the same code in initial button press.

How come?

[kaisellgren]

Ooh now it's working. Cool. All problems seem to be solved now

Now I need to figure out how to send http requests and how to get responses back.

[kaisellgren]

Okay everything is working great except I have slight problems...

Error	3	'GetStream' is not a member of 'Chatter.Client'.	C:\Documents and Settings\Kai\My Documents\Visual Studio 2008\Projects\Chatter\Chatter\Private.vb	9	38	Chatter

This is the error I keep getting.

I have a main form which is the client. In client I have a button "Open private chat window" which opens a private chat window. I have a private.vb form similar to my main chat window. The only problem is the above, my private.vb seems not to be able to use the connection code anymore, so:

How to make a new form/window to use existing connection used by main.vb?

[pippi]

Thanks for the excellent code snippets, this thread got me quite far.

However, i have a problem: I am transfering strings between the client and the server (both ways), and those messages then get interpreted. When things happen/events fire at roughly the same time (i guess its because of that), the messages get corrupted and mixed up. Is there a way to rewrite the SendMessage method so, that i can be sure the string gets sent and recieved completly and nothing gets in between?

Another question: i am sending lots of values of type double. The way i do it now, i convert the double to a string, use the SendMessage method from the example in this thread, and on the other end i am converting the string back to a double. There are a lot of conversions going on, is there a more efficient way of doing this with sockets?

Any hints appreciated,
P.

[Atheist]

Thanks for the excellent code snippets, this thread got me quite far.

However, i have a problem: I am transfering strings between the client and the server (both ways), and those messages then get interpreted. When things happen/events fire at roughly the same time (i guess its because of that), the messages get corrupted and mixed up. Is there a way to rewrite the SendMessage method so, that i can be sure the string gets sent and recieved completly and nothing gets in between?

Hmm. I've never had this happen to me, are you calling the Flush() method after each string being sent?
Have you made any other modifications or is the code on the first page of this thread basically what you have?

Edit: Are you saying that one clients message is mixed with another clients message? Or are two messages from the same client mixed together?

Another question: i am sending lots of values of type double. The way i do it now, i convert the double to a string, use the SendMessage method from the example in this thread, and on the other end i am converting the string back to a double. There are a lot of conversions going on, is there a more efficient way of doing this with sockets?

Any hints appreciated,
P.

I've never tried any of this so Im not 100% sure of how to go about it.
There's an overload of the StreamWriters Write method that'll let you write a double value directly to the stream. If you're only sending Doubles on the stream, you could modify the receiving end to only read 8 bytes at a time ( 1 double = 8 bytes), if you're sending doubles OR strings depending on the situation, it gets a bit more tricky. You'd have to add something like a header to your data before you send it that tells the receiving end what type of data its getting.
You'd have to modify the receiving end to

[pippi]

Atheist: yes, 2 message-strings from the same client mixed/appended, and also some messages from the server to the client. I will double check if id did something different than in your code you posted. I use the Flush() method too. Could it be problematic that the SendMessage method is called from different threads?

Thanks for your suggestion about the double values, i will check it out. I will still need to send strings too tho.

Regards,
Pippi

[Atheist]

The reason why 2 messages from the same client are concatenated is because a stream is open between the client and the server, and data can be pushed out continously. If one message is sent just after the other, they will most likely arrive at the receiving end at the same time. You'd need some character or other delimiter to mark the "end of message", so that you can separate one message from the other. I will update my example code with this implementation tomorrow.

[pippi]

Thanks a lot, Atheist.

[pippi]

I think what happens is that my server sends so many messages in such a short time, that too many messages are concatenated that the resulting string exceeds the 256 byte readbuffer of the clients. I guess due to this the clients dont recieve all data (some data will get lost when the server sends a string that exceeds the clients readbuffer, right?), and that some incomplete messages reach the clients messageRecieved method, where i want to interprete and react to incoming messages.

I guess i need to find a way to interprete concatenated messages and make sure that data is sent in such a way that the predefined size of the readbuffer will suffice.

[Atheist]

Yeah I was thinking of replacing that buffer with a loop that continously reads from the stream, appends everything thats being read to a stringbuilder, and when an "end of message" delimiter is found, it raises a "message received" event and passes the contents of the stringbuilder. It would then reset the stringbuilder and continue reading from the stream. This way nothing will be lost and you will get each message separately.
I am unfortunately not at home yet so I cant change my code example like i said, not until sunday evening swedish time.

[Atheist]

I have thrown together this example, its the ConnectedClient class, but you'd do the same in code on the client side.
I havent tested this at all, so it probably has some errors in it.

Public Class ConnectedClient
    Private mClient As System.Net.Sockets.TcpClient
 
    Private mUsername As String
    Private mParentForm As Form1
    Private readThread As System.Threading.Thread
 
    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 messageDelimiterIndex As Integer = Array.IndexOf(readBuffer, 13)
 
                If (messageDelimiterIndex > -1) Then
                    'If the value 13 (ControlChars.Cr) was found in the message, we have found the
                    'end of the current message, so what we need to do is add the last piece of the message
                    'to the stringbuilder, raise the dataReceived event, create a new blank stringbuilder,
                    'and append the remaining text to the new stringbuilder
                    sBuilder.Append(System.Text.Encoding.UTF8.GetString(readBuffer, 0, messageDelimiterIndex))
                    RaiseEvent dataReceived(Me, sBuilder.ToString)
                    sBuilder = New System.Text.StringBuilder
                    sBuilder.Append(System.Text.Encoding.UTF8.GetString(readBuffer, messageDelimiterIndex + 1, bytesRead - (messageDelimiterIndex + 1)))
                Else
                    'The value 13 was not found in the message, so we just append everything to the stringbuilder.
                    sBuilder.Append(System.Text.Encoding.UTF8.GetString(readBuffer, 0, bytesRead))
                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

As you can see, it uses the ControlChars.Cr as a message delimiter (byte value of 13).

[pippi]

I have thrown together this example, its the ConnectedClient class, but you'd do the same in code on the client side.
I havent tested this at all, so it probably has some errors in it.

Thanks for the code. Would a solution like this also solve the problem that its possible that the server (or the client) can send a concatenated string that is bigger than the readbuffer?

Regards,
P.

[Atheist]

Thanks for the code. Would a solution like this also solve the problem that its possible that the server (or the client) can send a concatenated string that is bigger than the readbuffer?

Regards,
P.

Yes, since this method will just keep appending to a stringbuilder until an end-of-message constant is found, you'd be able to send messages of practically unlimited length. (Oh well, atleast until the stringbuilders max capacity is reached)

[pippi]

Very nice, i will try that out. Thanks again, this is exactly what i needed.

[pippi]

That worked like a charm.

However, if i do too much calculations in the messageRecieved method in the client, while the client recieves lots of messages, it cant keep up and looses data. If i only have for example a message counter in the messageRecieved method, i dont loose any messages at all.

Im thinking of just adding the message to a queue in the messageRecieved method, and have a seperate thread work this queue and do all the other stuff in there. Maybe that helps.

Regards,
P.

[Atheist]

The MessageReceived subroutine is an eventhandler for the DataReceived event, which is raised on the same thread that reads from the stream. You should place very little actual code in that subroutine, and instead invoke methods to execute on the main thread when you want to perform any kind of calculations or UI integration.


Edit: silly typos gives my post a whole new meaning

[pippi]

I think i have found a problem with the new DoRead method (if i understand your code right): when there is more than 2 messages concatenated, it should send all messages to the messageRecieved method, it does however only send the first, and assumes that the second part is an incomplete message, while it is possible that there is more than 1 complete message in the readBuffer.

Sometimes i get 5 or more concatenated messages, so i will have to find a way to seperate them and send them all at once. *scrathcing head*

Regards,
P

[Atheist]

I think i have found a problem with the new DoRead method (if i understand your code right): when there is more than 2 messages concatenated, it should send all messages to the messageRecieved method, it does however only send the first, and assumes that the second part is an incomplete message, while it is possible that there is more than 1 complete message in the readBuffer.

Sometimes i get 5 or more concatenated messages, so i will have to find a way to seperate them and send them all at once. *scrathcing head*

Regards,
P

Oh well yeah I suppose you could just convert it all into a string and split it on each occurance of the end of message delimiter. Again this is untested code:

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(ControlChars.Cr) > -1) Then
 
                    'Since we know that the string contains our special delimiter (ControlChars.Cr) we can split the string on each occurance of it.
                    Dim subMessages() As String = message.Split(ControlChars.Cr)
 
                    '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
 
                    'ControlChars.Cr was not found in the message, so we just append everything to the stringbuilder.
                    sBuilder.Append(message)
                End If
            End If
        Loop
    End Sub

Might not even be the best way to go about it

[pippi]

Thanks, Atheist. I got it all working now, altho i have done it a bit differently. I just check if the last read byte is a message delimiter, and if not, i keep the last part of the message (i dont want to post it here in this forum-section, because i use C#).

Again, many thanks for your help.

[MrMakealotofsmoke]

hey im looking at this and im testing it out. I got 1 question, how do i send a message from the client to the server so the server sends it out to all the other clients connected?

Im using

SendMessage(txtMsg.Text)

on it but i want to use the username stuff like u said above so when multiple clients are on they know who is talking

Or should i just do

SendMessage(txtUsername.Text & ":" & txtMsg.Text)

also i set up a txtLog thing on the server so i can see what is being typed, but when the client sends data it reaches the server but the server doesnt send the data to the other clients

[Atheist]

Remember that you as the programmer is the designer of the protocol that your chat application uses. You decide what "commands" a client can send to the server, and how the server should react to a given command. In my example I only have 2 available commands for the clients: CONNECT and DISCONNECT. You'll have to make the server capable of receiving yet another command, that takes 2 more fields of data: sender name and message. Upon receiving this command it'd be appropriate to iterate through the connected clients and send a command to each one of them that notifies them of this new message.

[digitalcircuit36939]

I'm having trouble with getting the client to send a message to all the clients. I've tried several things, including making the client also a server to send messages to the server, which didn't work. Do you think you could post the entire project here?

[Edit]
I got it to work, but it only allows one user to talk to one other user.
Could you only get two users to work?

[Atheist]

I dont understand what you mean. Are you having problems with letting two clients chat with eachother?

[digitalcircuit36939]

Actually, I did get the clients to communicate by making each also a server, but I can not get more than two clients to chat at the same time.
1. The first chat program connects to the second chat client, and can send messages to the second.
2. Then the second chat program connects to the first, and can send messages to the first.

Using the original code, I could not get the server to receive messages from the clients. The server could only send messages to the clients. That's why I had to use the workaround mentioned above.

[Atheist]

If client nr1 has already connected to client nr2, theres no need for client nr2 to connect to client nr1 again, and create a second TCP connection. Data can be sent both ways through an the first existing TCP connection.

However, this is not the way you'd want to go about doing this.
In my example, it is possible for the clients to send data to the server, and for the server to send data to the clients. With these two basic abillities you can write a simple chat application.
In order for client nr1 to send messages to client nr2 through the server, client nr1 needs to send the message he wants client nr2 to receive to the server, along with something that specifies that the message is supposed to be delivered to client nr2. The server would then send the message on to client nr2, and specify that it came from client nr1.

This is, of course, a simple chat service. As long as the number of people using the service simultaneously isnt too great, it'll be alright. But if you want to write a distributed application for chatting where the number of users would be very high, you'd need to go with a client/server-p2p hybrid approach.