Classic ASP

Read an SSH Channel with a Byte Threshold

Demonstrates the Chilkat Ssh.ChannelReadAndPoll2 method, which works like ChannelReadAndPoll but also returns once newly processed data brings the total buffered data to or above a byte threshold. The arguments are the channel number, the poll timeout, and the threshold.

The integer return value is -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or channel close was processed, or — when greater than 0 — the total bytes currently buffered for the channel (not the bytes newly received by this call).

Background: The threshold makes it practical to stream large output in manageable chunks instead of buffering an entire multi-megabyte result. Treat it as a return threshold, not a hard cap: a complete SSH packet is buffered as a unit, so the amount returned can exceed what you asked for. Data already buffered before the call does not by itself trigger an immediate return.

Chilkat Classic ASP Downloads

Download Chilkat for Classic ASP

Classic ASP

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
success = 0

'  Demonstrates the Ssh.ChannelReadAndPoll2 method, which works like ChannelReadAndPoll but also
'  returns once the total buffered data reaches or exceeds a byte threshold.  The 1st argument is
'  the channel number, the 2nd is the poll timeout, and the 3rd is the byte threshold.

set ssh = Server.CreateObject("Chilkat.Ssh")

sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

'  Normally you would not hard-code the password in source.  You should instead obtain it
'  from an interactive prompt, environment variable, or a secrets vault.
password = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin",password)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

channelNum = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

'  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
'  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
'  echo typed commands back, and skips interactive login scripts.  The output is therefore
'  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
'  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
success = ssh.SendReqShell(channelNum)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

success = ssh.ChannelSendString(channelNum,"cat /var/log/syslog" & vbLf,"utf-8")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

'  Return when output goes quiet for 500ms, or once about 64KB has been buffered.  The
'  threshold is not a hard buffer limit -- a whole SSH packet may push the total above it.
pollTimeoutMs = 500
maxNumBytes = 65536
'  The return value is: -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or
'  channel close was processed, or the total number of buffered bytes when greater than 0.
result = ssh.ChannelReadAndPoll2(channelNum,pollTimeoutMs,maxNumBytes)
If (result = -1) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

If (result = -2) Then
    Response.Write "<pre>" & Server.HTMLEncode( "No channel data arrived before the timeout.") & "</pre>"
End If

If (result = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( "EOF or channel close was processed.  Buffered data may still remain.") & "</pre>"
End If

If (result > 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Total bytes buffered: " & result) & "</pre>"
End If

output = ssh.GetReceivedText(channelNum,"utf-8")
If (ssh.LastMethodSuccess = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( ssh.LastErrorText) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( output) & "</pre>"

ssh.Disconnect 

%>
</body>
</html>