writing a Telnet client with VB. NET

Question

Hi, I am trying to write a simple telnet client using VB.NET with Visual Studio 2005.

I am using System.Net.Sockets.

But I cant make it work yet.

What I need is:
To automate some tasks on UNIX server.
To achieve this, I need to login to unix (from within my app.) via telnet, and run some commands.
Thats all.

Anyone can help me with this ?

Thanks

Fede.

 

 

 

 

Answer 1

Is there a specific problem you are having with the socket communication.  If you can narrow down your question we will better be able to answer it.

Answer 2

yes,

I'am Using

System.Net.Sockets
tcpClient

By now i succeeded to connect to the unix server.

I recieve this as a response: "??↑??▼??#??'??".

I tried to parse it with Encoding.Ascii without success. I dont get anything.

How to negotiate the authentication process ?

 

Thanks

Fede

 

 

Answer 3

Hey,

Download this sample from

http://www.c-sharpcorner.com/UploadFile/tylerkline/TelnetScripting11282005001158AM/TelnetScripting.aspx?ArticleID=a8e0e439-14df-4d82-82ee-8cb4c110f9a0

Its just 1 source file that will compile to an assemply and you can use its public methods to script your telnet session. I had the same issue where I had to script a telnet session for a cisco interface using telnet. You may have to register to download the sample.

If your not able to figure it out, let me know and I can post some sample code.

 

Answer 4

Hi there,

 

I've the smae issue and I've downloaded the ScriptTelnet C# project from the URL provided above.

Now how do I implement using that class in VB.NET?

 

I apperciate any help in advance.

Answer 5

Ok.  The first thing you should do is make sure the downloaded project compiles ok.  Then create a new project, I would do just a Console app for testing, add a reference to the .dll file and then do something like the following:

Imports objActiveSolutions

Module Module1

Sub Main()

Dim ip As String = "66.xx.xx.xx"

Dim port As Integer = 23

Dim timeout As Integer = 10

'create the object supplying the parameters

Dim session As New ScriptingTelnet(ip, port, timeout)

Dim connected As Boolean = session.Connect() 'try to connect

If connected = True Then

'connected sucessfully

Dim startingPrompt As Integer = session.WaitFor("Username:")

If startingPrompt = 0 Then

'the username prompt was found so we send the username

'and wait to receive our password prompt

session.SendAndWait("testuser", "Password:")

'now send the password and wait for our next prompt

'in this sample I expect to receive a success message

session.SendAndWait("testpassword", "Success")

Else

Console.WriteLine("Username prompt was not found")

End If

Else

Console.WriteLine("Unable to connect to the server")

End If

End Sub

End Module

 

I hope you get the feel of how to use this component to script your session.

Answer 6

hey TDAVISJR thaks so much for the example above. 

 

I compiled and used the DLL as you suggested, but I'm getting an exception.  It makes a successful connection to the server. However it waits for the "login:" prompt, and the time out occure while waiting.  I tried with longer timeout values and that didn't resolve it.  Do you know what may be causing that exception?

 

Thanks for all the help.

Wekkaw

Answer 7

Well, other than making sure your looking for the correct prompt because it will time out if it don't find the prompt. Also, you could try stepping into the code and see where it fails. I'm not really an expert on the inner workings of this component. I used it and it worked. I don't think there is any contact info for the author of the code so you can shoot him an email, but you can double check that.  I don't know how much more I can help. Just do your best with it, if it doesn't work out then its back to the drawing board.

Answer 8

TDavisjr, thans so much for the help. I've tried stepping in but I'm not seeing anything yet.

I'll keep on working on it tho. Thanks again for putting me to the right direction.

 

Wekkaw

Answer 9

I im trying to write a Telnet client for pocket Pc...can you help me?

Answer 10

I am having the same issue as well.  I copied and pasted the prompt for "Username: " from the telnet window that I have, but it still does not work.

Anyone have any ideas?

Thanks,

Eric

Answer 11

Guys,

I don't know what is going on here. I was in the same situation you were all in until I found that component. I gave it a shot and it just worked. I have no clue why it worked for me and not for you all. Now, there are other components out there can can script telnet sessions; but of course they are not free. Good luck you all.

Answer 12

This code does not work for me either.  It does not seem to be sending messages properly.

Answer 13

I found something in http://www.codeproject.com/cs/internet/terminalcontrol.asp , look at the file TerminalControl.cs (negociating sequence commands)

Answer 14

Hello,

This is a very good control.

But how can I simulate "Enter" command into terminal ?

Thanks

Answer 15

TDAVIS or anyone that has this working in C#

could you either post or send me some source code of how you used the code you found? I am trying to do it but it isn't working for me for some reason.

Also did you just add the ScriptingTelnet class to your project or did you do it some other way? If some other way could I get information on how to do that as well.

Thanks

my email is fradam97 -at- gmail -dot- com if you would rather not post stuff.

Answer 16

el_Fede wrote:

yes, I'am Using System.Net.Sockets tcpClient By now i succeeded to connect to the unix server. I recieve this as a response: "??↑??▼??#??'??". I tried to parse it with Encoding.Ascii without success. I dont get anything. How to negotiate the authentication process ? Thanks Fede

To anyone having this problem and wanting to know why, I figured out that it is the Telnet server trying to negotiate with you.  If you run through the debugger (or print out) the actual byte numbers that correspond to those garbage symbols then look up negotiating a telnet connection online you will be able to figure it out.

Here is the site I found that helped me.

http://www.scit.wlv.ac.uk/~jphb/comms/telnet.html

Answer 17

the code was very useful for me and it worked. i wanted to convert this console application to a windows application. That is, if the username and password in the code matches, then i should get a form with two text boxes (- one for entering the command input (like show version) and another textbox for receiving output) and a command button. where should i change the code? in dll file or the console app code?

Answer 18

 

add VbCrLf

 

 

as in: Me.textbox1.text & vbcrlf

Answer 19

 I have exactly same problem and any VB.NET example there?

Answer 20

Real briefly, connect a TCP socket (stream) and read the "login:" prompt, send the userid, read the "Password:" prompt, send the password, then wait for the shell "#" prompt and send the command.

Telnet sends some basic header information which you can safely ignore. You just have to read a string off the stream and look for "login:", etc.

Also remember that UNIX systems (if that is what you are connecting to) uses "\n" (vbLf for VB guys) not "\r\n" (vbCrLf)

Answer 21

  Hi everyone,
I've got some problems with telneting a device too.
I can connect to a device authenticate with username and password, but can't  execute any command after that.
After sending some commands the receive buffer content hadn't changed. I suppose that I the commands are not send to the device.
The device I try to connect is MSAN - Huawei UA5000.
Can enyone help me?

Here is the code I use:

Sub Main()

Dim session As New System.Net.Sockets.TcpClient

Dim networkstream As Net.Sockets.NetworkStream

Dim bytes(session.ReceiveBufferSize) As Byte

Dim ne_data As String

Dim send_command1("username".Length) As Byte

Dim send_command2("password".Length) As Byte

Dim send_command3("enable".Length) As Byte

Dim send_command4("config".Length) As Byte

Dim send_command5("test".Length) As Byte

Dim send_command6("pots loop-line-test telno 074984046".Length + 2) As Byte

Dim i As Integer

session.Connect("10.240.73.132", 23)

If session.Connected Then

Debug.Print("connected")

If session.GetStream.CanRead Then

networkstream = session.GetStream

Debug.Print("Sending user name")

send_command1 = System.Text.Encoding.ASCII.GetBytes("username" & vbCrLf) 'with vbCrLf successfuly can sand username and password

networkstream.Write(send_command1, 0, send_command1.Length)

networkstream.Read(bytes, 0, CInt(session.ReceiveBufferSize))

ne_data = System.Text.ASCIIEncoding.ASCII.GetString(bytes)

Debug.Print("Device said:" & ne_data & vbCrLf)

Debug.Print("Sending password")

send_command2 = System.Text.Encoding.ASCII.GetBytes("msan" & vbCrLf)

networkstream.Write(send_command2, 0, send_command2.Length)

Threading.Thread.Sleep(1000) ' wait to receive data

networkstream.Read(bytes, 0, CInt(session.ReceiveBufferSize))

ne_data = System.Text.ASCIIEncoding.ASCII.GetString(bytes)

Debug.Print("Device said:" & ne_data & vbCrLf)

Debug.Print("Sending ENABLE") 'cannot send command to the device

send_command3 = System.Text.Encoding.ASCII.GetBytes("enable" & vbLf) '??? here is the problem ???

networkstream.Write(send_command3, 0, send_command3.Length)

Threading.Thread.Sleep(1000) ' wait to receive data

ne_data = System.Text.ASCIIEncoding.ASCII.GetString(bytes)

Debug.Print("Device said:" & ne_data & vbCrLf)

'some other code

networkstream.Close()

Else

Debug.Print("can't read")

End If

Else

Debug.Print("connection failed")

End If

session.Close()

If session.Connected Then

Debug.Print("still connected")

Else

Debug.Print("disconnected")

End If

End Sub

Answer 22

I am using this example and when it connect I get '??%' back so the wait for 'password:' times out.

Any ideas?

Answer 23

telent is pretty complex, certainly more than just opening and writing to a port.  i wrote an application to automate a bunch of tasks using telnet.

i used w3Sockets from Dimac.  it worked great.

DimacWebSite

Answer 24

is there any documentation for the dimac w3socket.dll?

Answer 25

Broken link?