Tcl

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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Tcl


load ./chilkat.dll

set success 0

#  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.

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
}

set channelNum [CkSsh_OpenSessionChannel $ssh]
if {$channelNum < 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

set success [CkSsh_SendReqExec $ssh $channelNum "uptime"]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  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.
CkSsh_put_ReadTimeoutMs $ssh 15000

set success [CkSsh_ChannelReceiveToClose $ssh $channelNum]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

set output [CkSsh_getReceivedText $ssh $channelNum "utf-8"]
if {[CkSsh_get_LastMethodSuccess $ssh] == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

puts "$output"

#  Send CLOSE for the channel.
set success [CkSsh_ChannelSendClose $ssh $channelNum]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  After a successful call, the channel is no longer reported as open.
if {CkSsh_ChannelIsOpen $ssh $channelNum} then {
    puts "Still open."
} else {
    puts "The channel is closed."
}

CkSsh_Disconnect $ssh

delete_CkSsh $ssh