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Tcl Examples

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(Tcl) TLS Connection within SSH Tunnel (Port Forwarding)

Demonstrates using Chilkat Socket to communicate to a TLS service through an SSH tunnel. This example will connect (through a port-forwarded SSH tunnel) to the GMAIL IMAP server via TLS and will receive the greeting.

Note: The Chilkat IMAP API provides direct support for using SSH tunneling with the IMAP protocol. This example serves only to demonstrate that, in general, TLS connections can be tunneled through SSH.

Chilkat Tcl Extension Downloads

Chilkat Tcl Extension Downloads

load ./chilkat.dll

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

set tunnel [new_CkSocket]

set sshHostname "www.my-ssh-server.com"
set sshPort 22

# Connect to an SSH server and establish the SSH tunnel:
set success [CkSocket_SshOpenTunnel $tunnel $sshHostname $sshPort]
if {[expr $success != 1]} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    exit
}

# Authenticate with the SSH server via a login/password
# or with a public key.
# This example demonstrates SSH password authentication.
set success [CkSocket_SshAuthenticatePw $tunnel "mySshLogin" "mySshPassword"]
if {[expr $success != 1]} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    exit
}

#  OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
#  Once the channel is obtained, the Socket API may
#  be used exactly the same as usual, except all communications
#  are sent through the channel in the SSH tunnel.
#  Any number of channels may be created from the same SSH tunnel.
#  Multiple channels may coexist at the same time.

# Connect to the GMAIL IMAP server via TLS (through the port-forwarded SSH tunnel)
# channel is a CkSocket

set maxWaitMs 4000
set useTls 1
set channel [CkSocket_SshOpenChannel $tunnel "imap.gmail.com" 993 $useTls $maxWaitMs]
if {[expr [CkSocket_get_LastMethodSuccess $tunnel] == 0]} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    exit
}

# If desired, visually inspect the LastErrorText to see that indeed the TLS
# protocol was run inside the SSH tunnel:
puts [CkSocket_lastErrorText $tunnel]

# The first thing an IMAP server does is to send a greeting terminated with a CRLF.
set imapGreeting [CkSocket_receiveToCRLF $channel]
if {[expr [CkSocket_get_LastMethodSuccess $channel] != 1]} then {
    puts [CkSocket_lastErrorText $channel]
    delete_CkSocket $channel

    delete_CkSocket $tunnel
    exit
}

puts "$imapGreeting"

# Close the connection to imap.gmail.com.  This is actually closing our channel
# within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
set success [CkSocket_Close $channel $maxWaitMs]
if {[expr $success != 1]} then {
    puts [CkSocket_lastErrorText $channel]
    delete_CkSocket $tunnel
    exit
}

delete_CkSocket $channel

# Finally, close the SSH tunnel.
set success [CkSocket_SshCloseTunnel $tunnel]
if {[expr $success != 1]} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    exit
}

puts "TLS SSH tunneling example completed."

delete_CkSocket $tunnel

 

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