How do I detect what application, if any, is listening on a given TCP port on Windows? Here's xampp doing this:
I'd prefer to do this in VB.NET, and I want to offer the user the option to close that app.
I don't have enough rep to comment on the accepted answer, but I would say that I think checking for an exception to occur is pretty bad practice!
I spent quite a while searching for a solution to a very similar problem, and was about to go down the P/Invoke GetExtendedTcpTable route when I happened upon IPGlobalProperties.
I haven't tested this properly yet, but something like this...
Imports System.Linq
Imports System.Net
Imports System.Net.NetworkInformation
Imports System.Windows.Forms
And then...
Dim hostname = "server1"
Dim portno = 9081
Dim ipa = Dns.GetHostAddresses(hostname)(0)
Try
' Get active TCP connections - the GetActiveTcpListeners is also useful if you're starting up a server...
Dim active = IPGlobalProperties.GetIPGlobalProperties.GetActiveTcpConnections
If (From connection In active Where connection.LocalEndPoint.Address.Equals(ipa) AndAlso connection.LocalEndPoint.Port = portno).Any Then
' Port is being used by an active connection
MessageBox.Show("Port is in use!")
Else
' Proceed with connection
Using sock As New Sockets.Socket(Sockets.AddressFamily.InterNetwork, Sockets.SocketType.Stream, Sockets.ProtocolType.Tcp)
sock.Connect(ipa, portno)
' Do something more interesting with the socket here...
End Using
End If
Catch ex As Sockets.SocketException
MessageBox.Show(ex.Message)
End Try
I hope someone finds this useful quicker than I did!
Dim hostname As String = "server1"
Dim portno As Integer = 9081
Dim ipa As IPAddress = DirectCast(Dns.GetHostAddresses(hostname)(0), IPAddress)
Try
Dim sock As New System.Net.Sockets.Socket(System.Net.Sockets.AddressFamily.InterNetwork, System.Net.Sockets.SocketType.Stream, System.Net.Sockets.ProtocolType.Tcp)
sock.Connect(ipa, portno)
If sock.Connected = True Then
' Port is in use and connection is successful
MessageBox.Show("Port is Closed")
End If
sock.Close()
Catch ex As System.Net.Sockets.SocketException
If ex.ErrorCode = 10061 Then
' Port is unused and could not establish connection
MessageBox.Show("Port is Open!")
Else
MessageBox.Show(ex.Message)
End If
End Try
this helped me :)
Related
I am writing a TCP listener (server) that needs to receive messages and send back an acknowledgement. Pretty basic stuff. There are literally dozens of examples out there, including MSDN, from which I copied much of my code. I can receive the message no problem. The problem comes when I try to send back the response. The sending client (Corepoint HL7 engine) reports the following error:
The connection was closed before a response was received
I have tested my service with my own TCP sending test app (written using code copied from MSDN) and it works. But when I receive messages from Corepoint, the response does not go back.
Below is my code. Does anyone have any idea why the NetworkStream.Write method is not actually sending the data (or why the client is not receiving it)? I've tried every idea I've found in other posts that are similar to my problem, and nothing is working. Am I doing something wrong, or is something wrong in the configuration of Corepoint?
Sub Main()
listenThread.Start()
End Sub
Private serverSocket As TcpListener
Dim listenThread As New Thread(New ThreadStart(AddressOf ListenForClients))
Private Sub ListenForClients()
Dim port As Int32 = '(pick a port #)
Dim localIP As IPAddress = 'enter your IP
serverSocket = New TcpListener(localIP, port)
serverSocket.Start()
While True 'blocks until a client has connected to the server
Dim client As TcpClient
If serverSocket.Pending Then
client = serverSocket.AcceptTcpClient
'tried these 2 settings with no effect
'client.NoDelay = True
client.Client.NoDelay = True
ProcessIncomingMessageSocketTCPClient(client) 'I was doing this in a separate thread but temporarily kept it on this thread to eliminate threading as the possible cause (but no luck)
client.Close()
Else
Threading.Thread.Sleep(1000) 'wait 1 second and poll again
End If
End While
End Sub
Private Sub ProcessIncomingMessageSocketTCPClient(ByRef objClient As TcpClient)
Dim strMessageText As String
Dim clientStream As NetworkStream
Dim msgBuffer(4096) As Byte
Dim numberOfBytesRead As Integer
Dim strChunk As String
Dim strCompleteMessage As New Text.StringBuilder
Dim sendBytes As Byte()
clientStream = objClient.GetStream()
Do
numberOfBytesRead = clientStream.Read(msgBuffer, 0, msgBuffer.Length)
strChunk = Encoding.ASCII.GetString(msgBuffer, 0, numberOfBytesRead)
strCompleteMessage.AppendFormat("{0}", strChunk)
Loop While clientStream.DataAvailable
strMessageText = strCompleteMessage.ToString
sendBytes = Encoding.ASCII.GetBytes("I received a message from you")
clientStream.Write(sendBytes, 0, sendBytes.Length)
objClient.Close() 'tried it with and without this line
End Sub
It turns out that nothing is wrong with my code. The TCP was and is working correctly. This application is an HL7 listener and I was missing the MLP wrapping around my ACK. As soon as I added that, the sending application accepted my ACK and all is good.
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!
I am making just a simple chat system using socket programming technique in vb.net .
It works fine on local network but how to use that over internet ..
I also try Port forwarding on my router ... May be my way is wrong .
Please tell me the correct way for port forwarding .. and tell me how to connect client to the server ???
Am i have to use a public IP of server system ???
the server side code is this :
Imports System.Net.Sockets
Module Module1
Sub Main()
Console.WriteLine("")
Dim clientListener As New TcpListener(12380)
clientListener.Stop()
clientListener.Start()
Console.WriteLine("")
Dim mySocket As Socket = clientListener.AcceptSocket()
Console.WriteLine("")
Dim recieveBuff(225) As Byte
mySocket.Receive(recieveBuff, recieveBuff.Length, SocketFlags.None)
Dim str As String = System.Text.Encoding.ASCII.GetString(recieveBuff, 0, recieveBuff.Length).Trim(Microsoft.VisualBasic.ChrW(0))
While Not str.StartsWith(".")
Console.WriteLine(str)
mySocket.Receive(recieveBuff, recieveBuff.Length, SocketFlags.None)
str = System.Text.Encoding.ASCII.GetString(recieveBuff, 0, recieveBuff.Length).Trim(Microsoft.VisualBasic.ChrW(0))
End While
Console.WriteLine("")
clientListener.Stop()
End Sub
End Module
and the client side code is this : (those both are console applications)
Imports System.Net.Sockets
Imports System.IO
Module Module1
Sub Main()
Try
Console.WriteLine("Connecting to localhost ")
Dim serverListener As New TcpClient("192.168.1.103", 12380)
Dim readStream As Stream = serverListener.GetStream
serverListener.SendBufferSize = 256
Console.WriteLine("Input Lines:")
Dim str As String = Console.ReadLine()
While 370
Dim sendBuff As Byte() = System.Text.Encoding.ASCII.GetBytes(str)
readStream.Write(sendBuff, 0, sendBuff.Length)
If str.StartsWith(".") Then
GoTo Done
End If
str = Console.ReadLine()
End While
Done: Console.WriteLine("Done")
Catch exp As Exception
Console.WriteLine("Exception: " + exp.ToString())
End Try
End Sub
End Module
You will need to use the public IP if the client is outside of your LAN.
First you need to enable port forwarding in the router, port should be lie between 49152 and 65535 and Address would be the private address of the server ex:"192.168.1.x"
Make sure you start listening your server in the new port (the one between 49152 and 65535)
then go to canyouseeme.org
and type the new port that you used and press check port
if the result was success than your configuration was correct and your server now is accessible via internet ,if the result was a red Error then you might done something wrong,probably a firewall problem, or you need to change the router.
if you get success then you must change this line in every client instead of the old one:
Dim serverListener As New TcpClient(YourPublicIpAdrees,NewPort)
To get your public ip address go here myip.
This is how to send a socket over internet, try it and comment your result.
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.
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.