Getting simultaneous messages from different clients - TCP/IP communication

[vbnewbieuser]

Hi! Please, can anyone help me? I'm doing a test by creating a chat program that receives data from multiple clients. Everything is working well. My problem is that when two clients send messages at the same time, I just get the message from one of the clients. Is there a way to get incoming messages at the same time sorted by order of arrival?

below, part of the Server code.

Public Sub LISTEN()
        Dim CLIENT As New NEWCLIENT
        While True
            Try
                CLIENT.SOCKETCLIENT = SERVER.AcceptSocket
                CLIENTIP = CLIENT.SOCKETCLIENT.RemoteEndPoint
                CLIENT.THREADCLIENT = New Thread(AddressOf READ)
                CLIENTS.Add(CLIENTIP, CLIENT)
                NEWCONEXION(CLIENTIP)
                CLIENT.THREADCLIENT.Start()
            Catch ex As Exception
            End Try
        End While
    End Sub

    Public Sub READ()
        Dim CLIENT As New NEWCLIENT
        Dim DATA() As Byte
        Dim IP As IPEndPoint = CLIENTIP
        CLIENT = CLIENTS(IP)
        While True
            If CLIENT.SOCKETCLIENT.Connected Then
                DATA = New Byte(1024) {}
                Try
                    If CLIENT.SOCKETCLIENT.Receive(DATA, DATA.Length, 0) > 0 Then
                        CLIENT.MSG = Encoding.UTF7.GetString(DATA)
                        CLIENTS(IP) = CLIENT

                        Datareceived(IP)


                    Else

                        Exit While
                    End If
                Catch ex As Exception

                    Exit While
                End Try
            End If
        End While
        Call ENDTHREAD(IP)
    End Sub

Private Sub DATARECEIVED(ByVal IDTerminal As IPEndPoint)
ListBox1.Items.Add(DATARECEIVED)
End Sub

[Sitten Spynne]

Wow. This coding style is very archaic. Please consider looking at the examples on MSDN and adopting a style like them. TYPING IN ALL CAPS MAKES IT VERY DIFFICULT TO READ. THERE ARE PSYCHOLOGICAL STUDIES THAT PROVE IT. AndAlternatingCapsMakeItEasier TOPICKOUTWORDSIFTHEREARENOSPACES. I know it's Visual "BASIC", but I think we've moved on from all-caps.

I can't answer definitively, because I don't know what the type "NEWCLIENT" is. If you don't show me the types your code uses, I can't make a good assertation of where problems lie.

This bit is very bad:

Catch ex As Exception
End Try

Your program throws exceptions to tell you something went wrong. This code says, "If something goes wrong, don't bother me". So if something is going wrong with the message you "aren't receiving", you've politely asked your program to shove it. That means it's probably happening and you don't know. The error message would be useful when it comes to understanding what is happening.

I can't make much progress. Your code looks like pseudocode because you aren't using any types I'm familiar with, and you're also making decisions that don't make any sense from an expert perspective. For example:

If CLIENT.SOCKETCLIENT.Receive(DATA, DATA.Length, 0) > 0 Then

If this is any Socket.Receive() I'm familiar with, the function is returning how many bytes it read. That may be only 10 or 15 bytes, but the array 'DATA' is 1024 bytes. So you're supposed to make sure you only try to decode that many bytes. But then:

CLIENT.MSG = Encoding.UTF7.GetString(DATA)

UTF7 is a very, very strange encoding. Almost no one uses it. Why did you choose this encoding?

That little bit of code, if written with familiar APIs, should look something like this:

Try
    Dim bytesRead = clientInfo.Client.Receive(buffer, buffer.Length, 0)
    If bytesRead > 0 Then
        Dim message As String = Encoding.UTF8.GetString(buffer, bytesRead, 0)
        clientInfo.Message = message
        ...

Like above, you don't do anything reasonable if this throws an exception, so you don't have a clue if it's working. Never, ever, ever write a "Catch ex As Exception" if you aren't logging or displaying what the exception does.

TL;DR:

Don't try to write your own chat client just yet. There are hundreds of tutorials online with examples. Download one of them, study it, and try transcribing it so you can learn how it works. After you've played with a few tutorials for a few days, try this again and see if it isn't easier.

Also, seriously. Lose the all-caps. I almost decided to ignore this thread because of it.