I'm connecting to a specific TCP port of a server, do stuff, and I need to disconnect at some point, then wait for the server to open its port again and reconnect.
My program loops forever.
To disconnect from the server, I sent from the server the string "TCP:OFF" and the close the port (server side). Whenever my program reads this line, I want it to close its connection and wait the server to open its port again. This is because of the TCP/IP protocol.
The problem is that the specific ASCII string sent from my server is not read until I put my mouse over my window (weird). At the end, I want my program to work by itself and minimized, without human intervention.
There must be a problem in the timing of my networkStream reading.
Code
While tcpClient.Connected() = False
Try
tcpClient.ReceiveTimeout = 1000
tcpClient.SendTimeout = 1000
tcpClient.Connect("192.168.10.100", 10003)
Console.WriteLine("Connection OK")
System.Threading.Thread.Sleep(1000)
Catch ex As Exception
Console.WriteLine("ERRORR : Server unreachable")
System.Threading.Thread.Sleep(1000)
End Try
End While
Dim networkStream As NetworkStream = tcpClient.GetStream()
If networkStream.CanRead And networkStream.DataAvailable Then
Try
ReadData = ""
Dim myReadBuffer As Byte() = New Byte(7) {}
Dim numberOfBytesRead = networkStream.Read(myReadBuffer, 0, myReadBuffer.Length)
ReadData = Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead)
Console.Write(ReadData & vbCrLf)
Catch ex As Exception
Console.Write("Error reading data")
End Try
End If
If ReadData = "TCP:OFF" Then
tcpClient.Close()
ReadData = ""
Console.WriteLine("Closing connection")
System.Threading.Thread.Sleep(5000)
tcpClient = New TcpClient
End If
I'm doing a Windows form program in latest Visual Studio.
Related
I made a Winforms application to work with 4 different machines by connecting with them via TCP/IP. Somehow, the connection sometimes seems disconnected and reconnecting after a short while. May I know is it I used too much TCP client and caused them congested??
Below is the function/method to connect those machine...with 4 of them different function names to connect each of the machine, but the code is more or less the same:
Public Async Sub connect_Machine_Ethernet(ByVal mainForm As Form1)
If Machine_COMPort.IsOpen Then
Machine_COMPort.Close()
End If
If (IsNothing(Machine_client)) Then
'do nothing, since obj is not created
Else
Try
Machine_client.GetStream.Close()
Machine_client.Close()
Catch exp As Exception
End Try
End If
Try
Machine_client = New TcpClient
Machine_client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, True)
Dim result = Machine_client.BeginConnect(Machine_ModuleIP_txt.Text, CInt(Machine_ModulePort_txt.Text), Nothing, Nothing)
result.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(1))
Machine_client.GetStream.BeginRead(Machine_ethernet_buffer, 0, Machine_ethernet_buffer.Length, AddressOf Machine_TCP_read, Machine_ethernet_buffer)
DisplayMsg("Machine Ethernet connection established")
manual_connection_LED.StateIndex = 3
Machine_client_isConnected = True
Machine_TCP_Reconnect_btn.Invoke(Sub() Machine_TCP_Reconnect_btn.Visible = False)
Catch ex As Exception
DisplayMsg("Error : Unable to connect to the Machine Ethernet connection")
manual_connection_LED.StateIndex = 0
Machine_client_isConnected = False
If (IsNothing(Machine_client)) Then
'do nothing, since obj is not created
Else
Try
Machine_client.GetStream.Close()
Machine_client.Close()
Catch exp As Exception
End Try
End If
End Try
End Sub
'Read Machine TCP message
Sub Machine_TCP_read(ByVal ar As IAsyncResult)
Try
Dim buffer() As Byte = ar.AsyncState
Dim bytesRead As Integer = Machine_client.GetStream.EndRead(ar)
Dim Message As String = System.Text.Encoding.ASCII.GetString(Machine_ethernet_buffer, 0, bytesRead)
If Message = "" Then
'----check connection
If Machine_client.Connected Then
Machine_client.Close()
connect_Machine_Ethernet(Me)
End If
Else
DisplayMsg("Input Received from machine : " & Message)
Process_machine_Feedback(Message) 'perform any data logic from the message
Machine_client.GetStream.BeginRead(Machine_ethernet_buffer, 0, Machine_ethernet_buffer.Length, AddressOf Machine_TCP_read, Machine_ethernet_buffer)
End If
Catch ex As Exception
DisplaySystemMsg(ex.Message)
DisplayMsg("Marking machine Ethernet disconnected from the server")
manual_connection_LED.StateIndex = 0
Machine_client_isConnected = False
Exit Sub
End Try
End Sub
'Send message to TCP
Public Sub Machine_TCP_send(ByVal str As String)
Try
sWriter = New StreamWriter(Machine_client.GetStream)
sWriter.WriteLine(Chr(2) & str & Chr(3)) 'add prefix suffix
sWriter.Flush()
DisplayMsg("Message send to the machine via TCP: " & str)
Catch ex As Exception
DisplayMsg("Error : Message failed to send to themachine!")
End Try
End Sub
I am using VB.net 2015 to try to communicate with a scale. I have somethings working where i can talk to scale a bit but i get random vb.net errors. Also most of the time I send the command and i get and error back from the scale so i send it again and the scale responds correctly and then i get a second response of an error.
It feels like the message i am trying to send is not getting there in one piece so i have to send it twice. Any help is great appreciated. i have so many hours into trying to make it work i am going blind.
Still learning and this is my first project using TCPClient and NetworkStream
Imports System.Net.Sockets
Public Class Form1
'Private ClientWritter As TCPControlWritter
'Public Client As TcpClient
Private port As Int32 = 1701
Private client As TcpClient
Dim stream As Net.Sockets.NetworkStream
'opens connection
Sub OpenConnection(ByVal server As [String])
Try
client = New TcpClient(server, port)
client.ReceiveTimeout = 200
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
'closes connection
Sub CloseConnection()
Try
If stream IsNot Nothing Then
stream.Close()
stream = Nothing
End If
client.Close()
client = Nothing
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
'takes the text from textbox and sends it to scale
Sub SendMesssage(ByVal message As [String])
Try
Dim data As [Byte]() = System.Text.Encoding.ASCII.GetBytes(message & vbCrLf)
' Get a client stream for reading and writing.
If stream Is Nothing Then stream = client.GetStream()
' Send the message to the connected TcpServer.
If stream.CanWrite Then
stream.Write(data, 0, data.Length)
stream.Flush()
End If
Debug.WriteLine("Sent: " & message)
' Receive the TcpServer.response.
' Buffer to store the response bytes.
data = New [Byte](256) {}
' String to store the response ASCII representation.
Dim responseData As String = ""
If stream.CanRead Then
' Read the first batch of the TcpServer response bytes.
Dim bytes As Int32 = stream.Read(data, 0, data.Length)
responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes)
Debug.WriteLine(responseData)
End If
Catch e As ArgumentNullException
Debug.WriteLine("ArgumentNullException: {0}", e)
Catch e As SocketException
Debug.WriteLine("SocketException: {0}", e)
End Try
txtMessage.Text = ""
txtMessage.Focus()
End Sub
'here is the data i get back from the scale. The "sent" lines are my input.
53 Ready for user
>
Sent: user admin
83 Command not recognized
>
83 Command not recognized
>
Sent: user admin
12 Access OK
>
83 Command not recognized
>
I'm trying to create a basic chat server-client program using TCP/IP and port forwarding in VB.NET. The code is derived almost entirely from Carlo De Silva's YouTube tutorials. I'm consistently having an issue connecting the two clients. When I open the client on my computer and another client on the other computer, I get the error "A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond [ip]:5757"
There are three different programs: the server, the client, and the client on the other end (the friend client.) The server and the client both use my local IP, which is accessed programmatically, so it couldn't be due to a typo. The friend client uses my external IP, which I've checked as of today (2018-09-09) and it is correct. I've set up port-forwarding on my router using TCP&UDP with my local IP, which was different when I checked it today, but I've updated the rule and the problem persists. Everything is done over port 5757. The firewall isn't an issue - I tried turning it off on the other computer and the friend client still fails to connect.
I've checked the port-forwarding tester on the website yougetsignal.com, which says that port 5757 is closed on both my local and external IP. But at the time of writing, I've currently got open the server and two client programs (both of which use my local IP,) and I am able to successfully send messages between those two client programs. So if they are able to send messages between the server and back, I don't understand why the website says that the port is closed on my local IP.
Can anyone help me work out why the friend client is failing to connect?
Server code:
Module MainModule
Dim _server As TcpListener
Dim _listOfClients As New List(Of TcpClient)
Dim hostName As String = System.Net.Dns.GetHostName
Dim ip As String = System.Net.Dns.GetHostEntry(hostName).AddressList(0).ToString
Dim extip As String = "86.25.175.94"
Dim port As Integer = 5757
Sub Main()
Console.Title = "SERVER"
Try
_server = New TcpListener(IPAddress.Parse(ip), port)
_server.Start()
Threading.ThreadPool.QueueUserWorkItem(AddressOf NewClient)
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
Console.ReadLine()
End Sub
Private Sub NewClient(state As Object)
Dim client As TcpClient = _server.AcceptTcpClient
Try
Threading.ThreadPool.QueueUserWorkItem(AddressOf NewClient)
_listOfClients.Add(client)
Dim ns As NetworkStream = client.GetStream
While True
'Creates a buffer
Dim toReceive(100000) As Byte
Dim length As Integer = ns.Read(toReceive, 0, toReceive.Length)
Dim text As String = Encoding.ASCII.GetString(toReceive, 0, length)
For Each c As TcpClient In _listOfClients
If c IsNot client Then 'Sends a message to every other client besides this one.
Dim nns As NetworkStream = c.GetStream 'New Network Stream
nns.Write(Encoding.ASCII.GetBytes(text), 0, text.Length)
End If
Next
Console.WriteLine(text)
Console.WriteLine()
'Sends a received message receipt.
Dim toSend() As Byte = Encoding.ASCII.GetBytes("Message Received...")
ns.Write(toSend, 0, toSend.Length)
End While
Catch ex As Exception
If _listOfClients.Contains(client) Then
_listOfClients.Remove(client)
End If
Console.WriteLine(ex.Message)
End Try
End Sub
End Module
Client code:
Module MainModule
Dim _client As TcpClient
Dim hostName As String = System.Net.Dns.GetHostName
Dim ip As String = System.Net.Dns.GetHostEntry(hostName).AddressList(0).ToString
Dim extip As String = "86.25.175.94"
Dim port As Integer = 5757
Sub Main()
Console.Title = "Chat Client (Host)"
Try
'Gets the local ip address
_client = New TcpClient(ip, port)
'This thread listens for receiving messages from the server.
Threading.ThreadPool.QueueUserWorkItem(AddressOf ReceiveMessages)
While True
'Starts a new stream
Dim ns As NetworkStream = _client.GetStream()
Dim message As String = Console.ReadLine()
Dim toSend() As Byte = Encoding.ASCII.GetBytes(message)
'Sends the message to the server
ns.Write(toSend, 0, toSend.Length)
End While
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
Console.ReadLine()
End Sub
Private Sub ReceiveMessages(state As Object)
Try
While True
'Starts a new network stream (receiving stream) to listen for any receiving messages.
Dim rs As NetworkStream = _client.GetStream
'Creates a buffer to receive text
Dim toReceive(100000) As Byte
'Reads anything coming in from the server.
Dim length As Integer = rs.Read(toReceive, 0, toReceive.Length)
'Converts the byte to text
Dim text As String = Encoding.ASCII.GetString(toReceive, 0, length)
Console.ForegroundColor = ConsoleColor.Green
Console.WriteLine(text)
Console.ResetColor()
Console.WriteLine()
End While
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
End Sub
End Module
The client and friend client are only different by one line of code:
_client = New TcpClient(extip, port) 'Friend client connects to external IP
_client = New TcpClient(ip, port) 'My client connects to local IP
Your issue is here:
_server = New TcpListener(IPAddress.Parse(ip), port)
The TcpListener(IPAddress, Int32) overload specifies which IP address to accept connections from, meaning it will accept connections from ONLY that IP (in this case your local address).
To fix this you've got to listen for connections at IPAddress.Any (equivalent to 0.0.0.0), which specifies that it should accept connections from any IP address.
_server = New TcpListener(IPAddress.Any, port)
I tried to use dont linger to reconnect to the server when losing connection
Public Class Agent
Dim bytes(1024) As Byte
Dim remoteEP As New IPEndPoint(IPAddress.Parse(My.Settings("HostIP").ToString), CType(My.Settings("HostPort"), Integer))
Dim permis As New SocketPermission(NetworkAccess.Connect, TransportType.Tcp, "", SocketPermission.AllPorts)
Dim S As New Net.Sockets.Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
If connect is successful it goeos to getdatadb, if not it goes to socketclose first and then it tries to connect again
Sub Connect()
Try
S.Connect(remoteEP)
Catch ex As Exception
socketclose()
S.Connect(remoteEP)
End Try
GetDataDb()
End Sub
with this to close the socket
Sub socketclose()
Dim myOpts As New LingerOption(True, 1)
S.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Linger, myOpts)
S.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.DontLinger, False)
S.Shutdown(SocketShutdown.Both)
S.Close()
End Sub
but it still shows exception
Once the socket has been disconnected, you can only reconnect again
asynchronously, and only to a different EndPoint. BeginConnect must
be called on a thread that won't exit until the operation has been
completed.
I don't know why dontlinger doesn't work.
I have a multithread(with Backgroundworker) TCP Server which is developed by VB.NET. It works very good when client and server at same machine. But when i connect to server from another computer which is at same LAN it works different. At this case it works good until i start to send messages consecutively (3-4 messages at a second). I send :
Hi
Hi
Hi
Hi
Hi
and server gets this messages such :
Hi
HiHi
HiHiHi
Hi
etc.
It's very interesting that this issue occurs only when client is at other computer at LAN.
Here is my listen Sub :
Sub listen_port6(ByVal b As BackgroundWorker)
Dim server As TcpListener
server = Nothing
Try
Dim port As Int32 = 8085
server = New TcpListener(IP, port)
server.Start()
Dim bytes(1024) As Byte
Dim data As String = Nothing
While True
Dim client As Sockets.TcpClient = server.AcceptTcpClient()
Dim ipend As Net.IPEndPoint = client.Client.RemoteEndPoint
PublicIP = ""
If Not ipend Is Nothing Then
PublicIP = ipend.Address.ToString
End If
b.ReportProgress(1)
Dim stream As NetworkStream = client.GetStream()
Dim i As Int32
Dim k As Short
For k = 0 To 1024
bytes(k) = 0
Next
i = stream.Read(bytes, 0, bytes.Length)
While (i <> 0)
data = ""
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i)
Debug.Print(data)
i = stream.Read(bytes, 0, bytes.Length)
End While
client.Close()
End While
Catch errore As Exception
Error_Print(errore.Message)
Finally
server.Stop()
End Try
End Sub
Thanks in advance