Creating a program that can pass built strings between two computers.
After digging and changing the syntax, I was finally able to see this socket exception:
System.Net.Sockets.SocketException (0x80004005): Only one usage of each socket address (protocol/network address/port) is normally permitted
at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Bind(EndPoint localEP)
at System.Net.Sockets.TcpListener.Start(Int32 backlog)
at System.Net.Sockets.TcpListener.Start()
at ChatProgFinal.chatForm.serverMode()
The port that I'm using is 11337. According to netstat, I'm not using that port, so I'm not certain how else I could be throwing this exception.
Here is my serverMode block:
Public Sub serverMode()
Try
Dim server As TcpListener = Nothing
server = New TcpListener(LocalIPEndPointAnyIP)
server.Start()
Dim incomingClient As TcpClient = server.AcceptTcpClient()
Do While isAlive = True And incomingClient.Connected = True
stream = incomingClient.GetStream()
If stream.CanRead Then
RaiseEvent DataReceived(stream)
End If
If incomingClient.Connected = False Then
RaiseEvent statusCheck("Disconnected")
isAlive = False
server.Stop()
End If
Loop
Catch e As Exception
RaiseEvent statusCheck(e.ToString)
Using outfile As New StreamWriter(docPath + "\log.txt")
outfile.Write(e.ToString)
End Using
Finally
stream.Close()
End Try
End Sub
Thank you for any advice you can provide on this.
Side question: I am not sure how to test/debug software that communicates between two computers through Visual Studio 2010. What I'm doing right now is publish it and deploy to a test VM. Anyone have any other methods I could use?
Along the lines of Hans's comment, you are probably calling serverMode more than once through the life of your program. The one thing I noticed is that in your finally block you are not calling .Stop on your server, which means its possible to exit serverMode without shutting it down. Once that happens, repeated calls to start the server will likely fail.
Related
I have a WCF Netnamedpipebinding from my application to an Office Addin. I have noticed that when the office app is busy doing something else that my application locks up when using a WCF method. I have added an example of my code. It appears that the code stops and waits with the channel.close method.
Is the solution to change channel.close to channel.BeginClose ?
What is the the state object I need to pass in to the BeginClose method?
Public Function RequestPersonStatus(ByVal id As String, ByVal email As String)
Using factory As New ChannelFactory(Of IToOffice)(New NetNamedPipeBinding(), New EndpointAddress("net.pipe://localhost/" + XXXXXX))
Dim OfficeChannel As IToOffice = factory.CreateChannel()
Try
OfficeChannel.RequestPersonStatus(id:=id, email:=email)
Catch ex As Exception
Return False
Finally
CloseChannel(CType(OfficeChannel, ICommunicationObject))
End Try
End Using
Return True
End Function
and the closeChannel
Private Sub CloseChannel(ByVal channel As ICommunicationObject)
Try
If channel.State = CommunicationState.Opened Then
Dim caller As New AsyncCallback(AddressOf callback)
channel.BeginClose(caller, New Object)
' channel.Close()
End If
Catch ex As Exception
Log(LogTypes.AllExceptions, "CloseChannel - Error closing the channel. ", ex.ToString)
Finally
channel.Abort()
End Try
End Sub
There seems to be a lot of discussion on what and when to clean up / Dispose / close down channels. I am just posting here what I am now doing and thus my answer to my question.
Private Sub CloseChannel(ByVal channel As ICommunicationObject)
Try
If channel.State <> CommunicationState.Closed AndAlso channel.State <> CommunicationState.Faulted Then
channel.BeginClose(Sub(asr)
Try
channel.EndClose(asr)
Catch
channel.Abort()
End Try
End Sub, Nothing)
Else
channel.Abort()
End If
Catch commEx As CommunicationException
channel.Abort()
Catch ex As Exception
channel.Abort()
Finally
End Try
End Sub
As far as I know, most of the cases like the timeout error/connection/communication error are caused by that the channel/client proxy is not properly closed. Putting the client proxy/Service Channel in a using block will eliminate the problem.
using (ServiceReference1.ServiceClient client=new ServiceClient())
{
var result = client.Test();
Console.WriteLine(result);
}
The Using statement is useful for automatically closed the service proxy/service communication channel after completing the invocation. Besides, Service client proxy is similar to the communication channel created by the ChannelFactory.
Feel free to let me know if there is anything I can help with.
I have an application done in VB.NET that listen on a specific UDP port and answer through the same port to the IP that send the packet.
It was working ok from a couple of years to the last month; now when try to answer crash due to socket error 10013.
I even try an older version that I know it was working too and get the same crash.
I try disabling Microsoft Security Essentials real time protection and Windows firewall and didn't work.
In the code I have the line
MyUdpClient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, True)
I have no clue about what to do, I'm lost.
Any idea how to solve this?
Edit:
Here's the code
#Region "UDP Send variables"
Dim GLOIP As IPAddress
Dim GLOINTPORT As Integer
Dim bytCommand As Byte() = New Byte() {}
#End Region
Dim MyUdpClient As New UdpClient()
Private Sub StartUdpBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartUdpBtn.Click
If StartUdpBtn.Tag = 0 Then
' If Not UdpOpen Then
StartUdpReceiveThread(CInt(ListeningPortLbl.Text))
'End If
Else
If ThreadReceive.IsAlive Then
ThreadReceive.Abort()
MyUdpClient.Close()
PrintLog("UDP port closed")
StartUdpBtn.Tag = 0
UdpOpen = False
StartUdpBtn.Text = "Start UDP"
End If
End If
If UdpOpen Then
StartUdpBtn.Tag = 1
StartUdpBtn.Text = "Stop UDP"
Else
StartUdpBtn.Tag = 0
StartUdpBtn.Text = "Start UDP"
TimerUDP.Enabled = False
TiempoUDP.Stop()
TiempoUdpLbl.Text = "--:--:--"
End If
End Sub
Private Sub StartUdpReceiveThread(ByVal Port As Integer)
Dim UdpAlreadyOpen As Boolean = False
Try
If Not UdpOpen Then
MyUdpClient = New UdpClient(Port)
MyUdpClient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, True)
UdpAlreadyOpen = True
Else
Me.Invoke(Sub()
TiempoUDP.Restart()
If TimerUDP.Enabled = False Then
TimerUDP.Enabled = True
End If
End Sub)
End If
ThreadReceive = New System.Threading.Thread(AddressOf UdpReceive)
ThreadReceive.IsBackground = True
ThreadReceive.Start()
UdpOpen = True
If UdpAlreadyOpen Then
PrintLog(String.Format("UDP port {0} opened, waiting data...", Port.ToString))
End If
Catch ex As Exception
PrintErrorLog(ex.Message)
PrintErrorLog(ex.StackTrace)
End Try
End Sub
Private Sub UdpReceive()
Dim receiveBytes As [Byte]() = MyUdpClient.Receive(RemoteIpEndPoint)
DstPort = RemoteIpEndPoint.Port
IpRemota(RemoteIpEndPoint.Address.ToString)
Dim BitDet As BitArray
BitDet = New BitArray(receiveBytes)
Dim strReturnData As String = System.Text.Encoding.ASCII.GetString(receiveBytes)
If UdpOpen Then
StartUdpReceiveThread(CInt(ListeningPortLbl.Text))
End If
PrintLog("From: " & RemoteIpLbl.Text & ":" & ListeningPortLbl.Text & " - " & strReturnData)
AnswersProcessor(strReturnData)
End Sub
Private Sub UdpSend(ByVal txtMessage As String)
Dim pRet As Integer
GLOIP = IPAddress.Parse(RemoteIpLbl.Text)
'From UDP_Server3_StackOv
Using UdpSender As New System.Net.Sockets.UdpClient()
Dim RemoteEndPoint = New System.Net.IPEndPoint(0, My.Settings.UDP_Port)
UdpSender.ExclusiveAddressUse = False
UdpSender.Client.SetSocketOption(Net.Sockets.SocketOptionLevel.Socket, Net.Sockets.SocketOptionName.ReuseAddress, True)
UdpSender.Client.Bind(RemoteEndPoint)
UdpSender.Connect(GLOIP, DstPort)
bytCommand = Encoding.ASCII.GetBytes(txtMessage)
pRet = UdpSender.Send(bytCommand, bytCommand.Length)
End Using
PrintLog("No of bytes send " & pRet)
End Sub
10013 is WSAEACCES, which is documented as follows:
Permission denied.
An attempt was made to access a socket in a way forbidden by its access permissions. An example is using a broadcast address for sendto without broadcast permission being set using setsockopt(SO_BROADCAST).
Another possible reason for the WSAEACCES error is that when the bind function is called (on Windows NT 4.0 with SP4 and later), another application, service, or kernel mode driver is bound to the same address with exclusive access. Such exclusive access is a new feature of Windows NT 4.0 with SP4 and later, and is implemented by using the SO_EXCLUSIVEADDRUSE option.
In the comments you mentioned:
I tried the program on a XP x32 and works ok but on Windows 7 x32/x64 don't, even if I disable the firewall and Microsoft Security Essentials Live Protection.
Maybe it sounds almost obvious but you could try to start your program in all of the available Windows XP compatibility modes. You didn't say that you already tried this but maybe you're lucky and the problem will be "solved" by this workaround.
If the problem still exists afterwards and considering the error code of 10013, I would try or check the following things:
I know you disabled "Microsoft Security Essentials" and the Windows Firewall, but double check whether there are other security related programs/services like anti virus protection, anti malware tools etc. running. It really sounds like something is blocking your socket creation/bind.
In case your program created log output/data which allows you to see exactly when it started to fail:
Any new software installed at that time?
Were Windows Updates (maybe automatically) installed at that time? Especially security updates regarding network security?
Any other noticeable changes in your environment? What about log entries in your Windows system log?
Just as a little test to verify if the error occurs only with your UDP socket: Try to use a TCP socket instead of UDP.
Start the machine in Windows Safe Mode with network support and execute your program from there.
Run your program on another Windows 7 machine and see if the same problem occurs there. It could be a valuable starting point (in terms of localization) to know if the problem occurs only on specific versions of Windows.
Single step through your code with a debugger and carefully watch what happens. Perhaps this can reveal some additional info on what's going wrong.
Maybe some of the ideas above can help you to track down the problem a little bit more. Good luck!
Is there a way to keep a TcpClient connection open constantly? I have an application which lets our users scan a carton, some database updates are performed, and a shipping label is sent to and printed from a wireless hip printer (model of printer is Zebra QLn420) which the user is using.
The application attempts to keep a connection to the wireless printer via the TcpClient connection, and multiple checks are made throughout processing to make sure the connection is good, before sending a generated ZPL to the printer for printing.
We have been having an issue with an occasional label missing, and it seems to be whenever the user stops scanning for a few minutes, then resumes. However, it is a semi-rare occurrence when a label is skipped, and as such is rather hard to reproduce (I haven't been able to replicate it myself, but I have seen it happen out in the warehouse).
I would like to know either if there is a way to make sure that the connection is always open (by "pinging" the device every so often), or if there is a way to get feedback that the data has been received and printed.
This is the code I'm calling to ensure a connection:
Public Function Connect(strIP As String, intPort As Integer) As Boolean
Try
'connect to printer via TcpClient, need ip address and port number
'connects without thread, hangs program for 10-20 seconds if printer is not turned on, replaced with code below to thread the connection and set timeout
For i As Integer = 1 To 2
If Not (client IsNot Nothing AndAlso client.Connected) Then
'uses ClientSocketParameters structure to pass to recursive function ConnectionReturned()
clntSockParams = New ClientSocketParameters
clntSockParams.addrs = strIP
clntSockParams.prt = intPort
'create client and call BeginConnect (attempts to connect on separate thread until TimeoutTime has elapsed)
client = New System.Net.Sockets.TcpClient
client.SendTimeout = 5000
client.ReceiveTimeout = 5000
'setup timer with timeout length and start, if timer goes past intTimeoutLength, the Timeout() function is called which closes everything and leaves client = Nothing
AddHandler TimeoutTime.Elapsed, AddressOf Timeout
TimeoutTime.Interval = intTimeoutLength
TimeoutTime.Start()
client.BeginConnect(strIP, intPort, New AsyncCallback(AddressOf ConnectionReturned), clntSockParams)
'keeps the program from doing anything else until BeginConnect either succeeds or fails (due to connect on separate thread)
Do While TimeoutTime.Enabled
System.Threading.Thread.Sleep(500)
Loop
End If
'if TimeoutTime is elapsed and client is Nothing, connection didn't happen, throw an error
If client Is Nothing Then
blnConnected = False
Else
blnConnected = True
Exit For
End If
Next
Catch ex As Exception
blnConnected = False
End Try
Return blnConnected
End Function
Private Sub ConnectionReturned(ByVal ar As System.IAsyncResult)
'this method is called from the client.BeginConnect line in Connect(), make sure timer is running
If TimeoutTime.Enabled Then
'ensure client is initialized
If client Is Nothing Then client = New System.Net.Sockets.TcpClient
'keep calling ConnectionReturned until client.Connected is true
If client.Connected Then
TimeoutTime.Stop()
Else
Dim actualParameters As ClientSocketParameters = DirectCast(ar.AsyncState, ClientSocketParameters)
client.BeginConnect(actualParameters.addrs, actualParameters.prt, New AsyncCallback(AddressOf ConnectionReturned), clntSockParams)
End If
End If
End Sub
Private Sub Timeout(ByVal sender As Object, ByVal e As EventArgs)
'this method is only called if TimeoutTime elapsed, which means no connection was made. close the client object if needed, set to Nothing, and stop TimeoutTime
If TimeoutTime.Enabled Then
Try
client.Close()
Catch ex As Exception
End Try
client = Nothing
TimeoutTime.Stop()
End If
End Sub
According to this question:
tcp client in vb.net not receiving the entire data response data from server
TcpClient is not always guaranteed to deliver all data to the other end of a connection, so if a more reliable connection method is available, that would be worth a try as well.
Please let me know if more information is needed. Thank you!
Originally I got the code for connecting via this link. I've modified it since because it would hang the application for 10-20 seconds if it took longer to connect. Code here is in C# and I translated to VB:
Send ZPL Commands via TCP/IP in C#
This is the link to the docs for the class:
TcpClient Class
Zebra printers have a timeout setting on TCP that I think has a 3 or 5 minute default. The first thing to do is to turn that timeout off. There will still be other reasons that the printer would disconnect so you will need to handle that as well.
embed this into your program:
! U1 setvar "wlan.ip.timeout.enable" "off"
Make sure you send a CR/LF before and after that line.
if you send a query after your format you can know that the whole format made it to the printer. Something like the following would work:
! U1 getvar "device.uptime"
That's not a sane solution. A sane solution is this: If a label isn't completely sent to the printer because the connection failed, make a new connection and send the label.
I am new to programming in vb.net. I have come a long ways in my development and understanding of vb, but there is one hurtle I can not seem to fix. I am hosting an ftp server on my pc and I am making an app for it to connect to my server and download files. The problem with all the sample code is that everyone ASSUMES the server WILL be ONLINE. My pc may not be running 24/7 and I also may not have the ftp service running.In the first case it shouldnt even register that it is connected. In the second case, it WILL say that is connected b/c the pc is on, but it will return that the machine ou are trying to connect to is actively refusing the connection. Is there a way to TRULY check if the program is indeed connected to the server WITHOUT generating a bunch of Exceptions in the debugger? All I want is a call like:
Dim ftponline As Boolean = False 'Set default to false
ftponline = checkftp()
If ftponline Then
'continue program
Else
'try a different server
End If
So it would be a function called checkftp that returns a boolean value of true or false.
Here is my info:
Using Visual Studio 2010 Pro
Using .Net framework 4
Can anyone help?
Thanks!
I have tried the rebex ftp pack as well as the Ultimate FTP Pack.
Here is the updated code:
Public Function CheckConnection(address As String) As Boolean
Dim logonServer As New System.Net.Sockets.TcpClient()
Try
logonServer.Connect(address, 21)
Catch generatedExceptionName As Exception
MessageBox.Show("Failed to connect to: " & address)
End Try
If logonServer.Connected Then
MessageBox.Show("Connected to: " & address)
Return True
logonServer.Close()
Else
Return False
End If
End Function
Public Sub ConnectFtp()
types.Clear()
models.Clear()
ListBox1.Items.Clear()
ListBox2.Items.Clear()
TextBox2.Clear()
Dim request As New Rebex.Net.Ftp
If CheckConnection(*) Then
Dim tempString As String()
request.Connect(*)
request.Login(*, *)
request.ChangeDirectory("/atc3/HD_Models")
Dim list As Array
list = request.GetNameList()
Dim item As String = ""
For Each item In list
tempString = item.Split(New Char() {" "c})
If types.Contains(tempString(0)) = False Then
types.Add(tempString(0))
End If
If models.Contains(item) = False Then
models.Add(item)
End If
Next
request.Disconnect()
request.Dispose()
ElseIf CheckConnection(*) Then
request.Connect(*)
request.Login(*, *)
request.ChangeDirectory(*)
Dim list2 As Array
list2 = request.GetNameList()
Dim item2 As String = ""
Dim tempString2 As String()
For Each item2 In list2
MessageBox.Show(item2)
tempString2 = item2.Split(New Char() {" "c})
If types.Contains(tempString2(0)) = False Then
types.Add(tempString2(0))
End If
If models.Contains(item2) = False Then
models.Add(item2)
End If
Next
request.Disconnect()
request.Dispose()
End If
End Sub
No matter what I do, the second server will not connect. I even put a messagebox to show what items were being returned in the second server, but there are no messageboxes apearing when I run the program with my server offline. Is there anyone who can help?
If your code is designed with proper exception catching, it shouldn't be generating a "bunch" of exceptions. The first exception you catch should be your indication that the connection failed and your code should cease attempting to communicate at that point. If for some reason you really need to check the connectivity before attempting the FTP connection, you should be able to simply attempt to synchronously open a TCP socket to the FTP server's port. If that works, it's up and running.
You could simply open a socket to the server's IP address on Port 21 (assuming default FTP port).
I'm not much of a VB.Net programmer, but here's a link to sample code:
http://vb.net-informations.com/communications/vb.net_Client_Socket.htm
If you can establish the socket connection, you know that something is listening on that port (though you have not yet proven it's an FTP server, or that it will accept your login credentials...).
If you wish to simply avoid exceptions in the debugger, you could place the connection code in a method and apply the DebuggerHidden attribute to that method.
I'm using TCP socket connetion between a server program and a client program. Multiple client programs shall connect to the same port. The problem is that if I close a client program I get the following error on the server-program:
System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
http://i55.tinypic.com/nh135w.png
If I handle this by a try/catch, I am then not able to re-connect with the client-program, as it gives the following error (in the client program):
No connection could be made because the target machine actively refused it 127.0.0.1: 1234
Below is the listener code in the server program. I hope to get some help to understand how I can handle client program shutdown/restart&reconnect without the server program failing..
' This is the callback function for TcpClient.GetStream.Begin, It begins an asynchronous read from a stream.
Private Sub DoRead(ByVal aread As IAsyncResult)
Dim BytesRead As Integer
Dim strMessage As String
' Try
' Ensure that no other threads try to use the stream at the same time.
SyncLock _client.GetStream
' Finish asynchronous read into readBuffer and get number of bytes read.
If Client.Connected Then
BytesRead = _client.GetStream.EndRead(aread)
End If
End SyncLock
' Convert the byte array the message was saved into, minus one for the Chr(13) (carriage return).
strMessage = Encoding.ASCII.GetString(readBuffer, 0, BytesRead - 1)
ProcessIncoming(strMessage)
' Ensure that no other threads try to use the stream at the same time.
SyncLock Client.GetStream
' Start a new asynchronous read into readBuffer.
Client.GetStream.BeginRead(readBuffer, 0, READ_BUFFER_SIZE, AddressOf DoRead, Nothing)
End SyncLock
'Catch e As Exception
' ' This triggers if userlist is found empty
' ' Then gives problem, as it cant close the connection or something.. ??
' Debug.Print("UserConnection.DoRead Exception: " & e.ToString)
' CloseConnetion("Error: Stream Reciever Exception")
'End Try
End Sub
You don't. You're the server. You close the socket and forget about it. If the client wants more service it is up to him to reconnect.