B4X

Send CLOSE on an SSH Channel

Demonstrates the Chilkat Ssh.ChannelSendClose method, which sends an SSH CLOSE message for a channel and immediately marks it locally closed. The only argument is the channel number. It does not wait for remote EOF, remote CLOSE, or an exit status.

Background: CLOSE shuts down both directions of the channel, unlike EOF which closes only your side. Because the call returns without waiting for the remote side to acknowledge, it does not guarantee the remote process has terminated — so retrieve any output and exit status you care about before calling it. Afterward ChannelIsOpen reports false, though NumOpenChannels may still count the channel until final remote-close processing.

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Dim success As Boolean = False

'  Demonstrates the Ssh.ChannelSendClose method, which sends an SSH CLOSE message for a channel
'  and immediately marks it locally closed.  The only argument is the channel number.  It does
'  not wait for remote EOF, remote CLOSE, or an exit status.

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, "uptime")
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


Dim output As String = ssh.GetReceivedText(channelNum, "utf-8")
If ssh.LastMethodSuccess = False Then
    Log(ssh.LastErrorText)
    Return
End If

Log(output)

'  Send CLOSE for the channel.
success = ssh.ChannelSendClose(channelNum)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  After a successful call, the channel is no longer reported as open.
If ssh.ChannelIsOpen(channelNum) Then
    Log("Still open.")
Else
    Log("The channel is closed.")
End If


ssh.Disconnect