Tcl

Check Whether an SSH Channel is Open

Demonstrates the Chilkat Ssh.ChannelIsOpen method, which reports whether a channel number identifies a channel Chilkat currently considers open for application I/O. The only argument is the channel number. This example checks the channel before and after sending CLOSE.

Background: Because one SSH connection can carry many channels with independent lifetimes, code that manages several needs a way to ask whether a given one is still usable. This returns false for invalid or nonexistent channel numbers, after a local Disconnect, once remote closure is processed, and immediately after ChannelSendClose — which marks the channel locally closed without waiting for the remote side.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the Ssh.ChannelIsOpen method, which reports whether a channel number identifies
#  a channel Chilkat currently considers open for application I/O.  The only argument is the
#  channel number.

set ssh [new_CkSsh]

set sshPort 22
set success [CkSsh_Connect $ssh "ssh.example.com" $sshPort]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  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.
set password "mySshPassword"

set success [CkSsh_AuthenticatePw $ssh "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  Open a session channel.  A negative return value indicates failure.
set channelNum [CkSsh_OpenSessionChannel $ssh]
if {$channelNum < 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

if {CkSsh_ChannelIsOpen $ssh $channelNum} then {
    puts "The channel is open."
} else {
    puts "The channel is not open."
}

#  Send CLOSE, which immediately marks the channel locally closed.
set success [CkSsh_ChannelSendClose $ssh $channelNum]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

if {CkSsh_ChannelIsOpen $ssh $channelNum} then {
    puts "Still open."
} else {
    puts "The channel is now closed."
}

CkSsh_Disconnect $ssh

delete_CkSsh $ssh