B4X

Get Text Received on an SSH Channel

Demonstrates the Chilkat Ssh.GetReceivedText method, which decodes and returns all text currently accumulated in a channel's normal receive buffer. The first argument is the channel number and the second is the charset. The receive buffer is cleared after the text is returned.

Background: This is the retrieval half of the read-then-get pattern: a Channel* read or receive call fills the buffer, and this hands you the text. Because the buffer is cleared on retrieval, each call returns only what arrived since the last one. A valid channel with nothing buffered returns an empty string successfully, so an empty result is not an error. Retrieve text promptly after a channel completes, before other SSH operations can discard the completed channel record.

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Dim success As Boolean = False

'  Demonstrates the Ssh.GetReceivedText method, which decodes and returns all text currently in
'  a channel's normal receive buffer.  The 1st argument is the channel number and the 2nd is the
'  charset.  The receive buffer is cleared after the text is returned.

Dim ssh As ChilkatSsh
ssh.Initialize("ssh")

Dim sshPort As Int = 22
success = ssh.Connect("ssh.example.com", sshPort)
If success = False Then
    Log(ssh.LastErrorText)
    Return
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.
Dim password As String = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin", password)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


Dim channelNum As Int = ssh.OpenSessionChannel
If channelNum < 0 Then
    Log(ssh.LastErrorText)
    Return
End If


success = ssh.SendReqExec(channelNum, "cat /etc/hostname")
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
'  it, this call waits forever if the server never sends channel close.
ssh.ReadTimeoutMs = 15000

success = ssh.ChannelReceiveToClose(channelNum)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  Retrieve the accumulated output.  A valid channel with no buffered data returns an empty
'  string successfully.
Dim output As String = ssh.GetReceivedText(channelNum, "utf-8")
If ssh.LastMethodSuccess = False Then
    Log(ssh.LastErrorText)
    Return
End If

Log(output)

ssh.Disconnect