[RESOLVED] TCP/IP Problem

Hi Guys! Good Day. Need to ask some help again. :)

I am developing a client side application that writes a COMMANDS and listens a RESULT.

Now, the server side is made from perl codes..

The task is simple...

Declare Global Variable:

Code:

---

    Private _TcpClient As New TcpClient
    Private _NetStream As NetworkStream

---

1. Connect to the Server

Code:

---

Private Sub Connect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Connect.Click
        Try
            _TcpClient = New TcpClient
            _TcpClient.Connect("10.0.28.99", 7890) 
        Catch ex As Exception
            Console.WriteLine(Err.ToString())
        End Try
    End Sub

---

2. Sends Command

Code:

---

    Private Sub Send_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Send.Click
        _NetStream = Nothing
        _NetStream = _TcpClient.GetStream

        Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes("22,REGIST,000012\n")
        _NetStream.Write(sendBytes, 0, sendBytes.Length - 1)
    End Sub

---

3. Receive Result automatically

Code:

---

    Private Sub ThreadOnRecieve
 Do
            Dim bytes(_TcpClient.ReceiveBufferSize) As Byte

            _NetStream.Read(bytes, 0, CInt(_TcpClient.ReceiveBufferSize))

            Dim returndata As String = Encoding.ASCII.GetString(bytes)

            ReturnLabel.Text = returndata
        Loop
    End Sub

---

4. Disconnect to the Server

Code:

---

    Private Sub Disconnect
 _TcpClient.Close()
    End Sub

---

Now, the problem are:
1. I Am definitely a newbie about TCP/IP
2. I could not send a command until i do this:

Code:

---

    _NetStream.Flush()
    _NetStream.Close()

---

but, when i did that. my stream are gone and i am not able to send another command. And when i tried to reconnect again, the server no longer accepts me... seems that my previous connection was still up..

Hope you can enlightens me.. Thanks guys! :)

First up, this is from the documentation for the NetworkStream.Flush method:

Quote:

---

The Flush method implements the Stream.Flush method; however, because NetworkStream is not buffered, it has no affect on network streams. Calling the Flush method does not throw an exception.

---

It sounds like the issue is more likely at the receiving end, like it is waiting for a specific terminator or the like. I've used a TcpClient and its NetworkStream before and I definitely didn't have to close the stream to receive data at the other end.

Hi JM,

I was actually expecting not to close my stream.. but nothing happens when i issued my Command until I close the Stream or TCPClient.

Yes, i think the receiver is still expecting more until it was closed.

But I have tested it on using Telnet and I have no issues about it, it works fine...

Any work around we can do??

Have you tried sending a \r\n on the end of your message, rather than just \n?

Ah, now I see the issue. I didn't even notice that "\n" in the string until I read EG's post.

The issue is exactly as I said: the receiver is waiting for a terminator and you're not sending one. What you're sending there are the two characaters '\' and 'n', not the one character '\n'. VB doesn't understand those C-style escape sequences. That "\n" would work in C# but not in VB. If you want to send a line terminator then you would use the ControlChars class:

vb.net Code:

Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes("22,REGIST,000012" & ControlChars.Lf)

ControlChars.Lf is equivalent to "\n". For "\r\n" you can use ControlChars.CrLf or ControlChars.NewLine.

WOW! Thanks JM and Evil_Girrafe!

I have no idea about the ControlChars.Lf..

haha! it worked!

Now the next step is how will i get the reply?

for every command i send there is a corresponding reply.

should i run a Thread or what? :)

If sending and receiving the messages is quite quick then it's probably not necessary to use multiple threads. If it's likely to take a while then it might not be a bad idea. The NetworkStream supports multi-threading inherently, via its asynchronous methods.

Ok! I'll try that asych method. Thanks! :)

I'll keep you guys posted.

If you want to see an example of asynchronous methods in action with a TcpClient, follow the CodeBank link in my signature and check out my Asynchronous TCP thread.

Yes JM, I've already done my research and checked your CodeBank even before I created the thread here.. ;)

Very useful! :) Keep it up!

Finished! Thanks a lot JM and Evil_Giraffe!

Resolved!