B4X

Check Whether SSH Channel CLOSE Was Received

Demonstrates the Chilkat Ssh.ChannelReceivedClose method, which reports whether an SSH CLOSE message has been received for a channel. The only argument is the channel number. Remote CLOSE is distinct from EOF and closes the channel in both directions.

Background: Remote CLOSE is the definitive end of a channel's life. Once it is processed, ChannelIsOpen becomes false and the channel is normally removed from NumOpenChannels. Checking it distinguishes "the server finished sending output" (EOF) from "the channel is fully finished" (CLOSE) — which is what you want before concluding a remote command has completely wrapped up.

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Dim success As Boolean = False

'  Demonstrates the Ssh.ChannelReceivedClose method, which reports whether an SSH CLOSE message
'  has been received for a channel.  The only argument is the channel number.  Remote CLOSE is
'  distinct from EOF and closes the channel in both directions.

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, "ls -l /tmp")
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


'  The server may send EOF before CLOSE.  During that interval EOF is True while CLOSE is
'  still False.
If ssh.ChannelReceivedEof(channelNum) Then
    Log("EOF received.")
End If


If ssh.ChannelReceivedClose(channelNum) Then
    Log("Remote CLOSE received -- the channel is closed in both directions.")
Else
    Log("No remote CLOSE received.")
End If


ssh.Disconnect