(VB.NET) Multiple SendReqExec on Same Connection

Shows how to execute a series of commands on an SSH server and retrieve each command's output (using SendReqExec). Each call to SendReqExec requires its own logical channel. This is not a separate SSH connection -- it's simply a new session channel on the existing SSH connection.

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' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim ssh As New Chilkat.Ssh

' Hostname may be an IP address or domain:
Dim hostname As String = "172.16.16.46"
Dim port As Integer = 22

Dim success As Boolean = ssh.Connect(hostname,port)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' If receiving output from a command stalls for more than 5 seconds, then stop waiting.
ssh.IdleTimeoutMs = 5000

' Authenticate using login/password:
success = ssh.AuthenticatePw("myLogin","myPassword")
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Open a session channel.  (It is possible to have multiple
' session channels open simultaneously.)
Dim channelNum As Integer = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Request a directory listing on the remote server:
' If your server is Linux/UNIX, change the string from "dir" to "ls"
' Note: Some SSH servers require a CRLF instead of a bare-LF
Dim cmd As String = "ls -al" & vbLf
success = ssh.SendReqExec(channelNum,cmd)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Read whatever output may already be available on the
' SSH connection.  ChannelReadAndPoll returns the number of bytes
' that are available in the channel's internal buffer that
' are ready to be "picked up" by calling GetReceivedText
' or GetReceivedData.
' A return value of -1 indicates failure.
' A return value of -2 indicates a failure via timeout.

' The ChannelReadAndPoll method waits
' for data to arrive on the connection usingi the IdleTimeoutMs
' property setting.  Once the first data arrives, it continues
' reading but instead uses the pollTimeoutMs passed in the 2nd argument:
' A return value of -2 indicates a timeout where no data is received.
Dim pollTimeoutMs As Integer = 2000
Dim n As Integer = ssh.ChannelReadAndPoll(channelNum,pollTimeoutMs)
If (n < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Close the channel:
success = ssh.ChannelSendClose(channelNum)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Perhaps we did not receive all of the commands output.
' To make sure,  call ChannelReceiveToClose to accumulate any remaining
' output until the server's corresponding "channel close" is received.
success = ssh.ChannelReceiveToClose(channelNum)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Get the accumulated output of the command:
Dim cmdOutput As String
cmdOutput = ssh.GetReceivedText(channelNum,"ansi")
If (ssh.LastMethodSuccess = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


' Display the remote shell's command output:
Debug.WriteLine(cmdOutput)
Debug.WriteLine("----")

' -----------------------------------------------------------------
' Now for the 2nd SendReqExe (on the same connection,
' but on a separate logical channel).
' -----------------------------------------------------------------

channelNum = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


cmd = "nslookup chilkatsoft.com" & vbLf
success = ssh.SendReqExec(channelNum,cmd)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


pollTimeoutMs = 2000
n = ssh.ChannelReadAndPoll(channelNum,pollTimeoutMs)
If (n < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


success = ssh.ChannelSendClose(channelNum)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


success = ssh.ChannelReceiveToClose(channelNum)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


cmdOutput = ssh.GetReceivedText(channelNum,"ansi")
If (ssh.LastMethodSuccess = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


Debug.WriteLine(cmdOutput)