(Tcl) Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method.

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 sock [new_CkSocket]

# --------------------------------------------------------------------
# This example uses the public TCP/TLS echo service at https://tcpbin.com/
# --------------------------------------------------------------------

# The echo server at tcpbin.com expects to receive TCP connections on port 4242, and TLS connections on port 4243.
# We could simply connect to port 4243 using TLS like this.
# However, further below, this example shows how to initially make a TCP connection, and then convert the connection to TLS.
set useTls 1
set port 4243
set maxWaitMs 5000
set success [CkSocket_Connect $sock "tcpbin.com" $port $useTls $maxWaitMs]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $sock]
    delete_CkSocket $sock
    exit
}

# OK, we have a TLS connection.
# Note: The server chooses the TLS protocol version. 
# We can see the version of the TLS connection that was established:
puts "TLS version: [CkSocket_tlsVersion $sock]"

CkSocket_Close $sock $maxWaitMs

# ---------------------------------------------------------------------
# Now we'll do the same, except first we connect to port 4243 using TCP,
# and then convert the connection to TLS.
# 
# This may seem pointless, and it is for the case w/ this server.  However, there could be situations
# where you're interacting with a server of some kind where there is a need to convert to/from TLS.
# (This is common internal to many protocols, such as SMTP, IMAP, FTP, etc., and it is often called "explicit" SSL/TLS)

# Connect again, except this time useTls is 0, so we only have a simple TCP connection after this call.
set useTls 0
set success [CkSocket_Connect $sock "tcpbin.com" $port $useTls $maxWaitMs]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $sock]
    delete_CkSocket $sock
    exit
}

# Convert the existing TCP connection to TLS.
# (The method name uses "SSL" because long ago, at the time of initial development, TLS 1.0 did not yet exist.)
set success [CkSocket_ConvertToSsl $sock]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $sock]
    delete_CkSocket $sock
    exit
}

# OK, we now have a TLS connection.
# Again, we can see the TLS version:
puts "TLS version: [CkSocket_tlsVersion $sock]"

CkSocket_Close $sock $maxWaitMs

delete_CkSocket $sock