(Tcl) Bidirectional Sockets (TLS or non-TLS, simultaneous reading and writing a connection)

This example demonstrates how to simultaneously read/write on a single socket connection.

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load ./chilkat.dll

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

set tlsRead [new_CkSocket]

# We'll just use an HTTPS server for this example...
set bUseTls 1
set maxWaitMs 5000
set success [CkSocket_Connect $tlsRead "www.chilkatsoft.com" 443 $bUseTls $maxWaitMs]
if {$success != 1} then {
    puts [CkSocket_lastErrorText $tlsRead]
    delete_CkSocket $tlsRead
    exit
}

# Chilkat classes are thread-safe.  This means that only one method call can be active
# at a time for a given object instance.  It would seem that this would prevent the possibility
# to simultaneously read/write a given connection because it would require two method calls
# to be simultaneously active: one for reading and one for writing.
# 
# There's a trick to doing it...
# 
# The CloneSocket method is provided to get a new object instance that shares the same socket
# connection.  This allows for the coarse-grained object-level thread safety to be maintained, 
# while finer-grained thread-safety mechanisms keep things kosher internally.

# One object will be used for reading, and the cloned socket is used for writing.
# It doesn't matter which --  you can use the cloned socket for reading or the original for writing.
# However.. if you try to read simultneously from both the original and cloned objects at the same
# time, then one will block until the other finishes.  (This is because of the finer-grained thread
# safety internally.)  The same is true if you try to write both socket objects simultaneously.

# tlsWrite is a CkSocket
set tlsWrite [CkSocket_CloneSocket $tlsRead]

# Let's start an async read on the socket.  Nothing will be arriving until we actually send the GET
# request and the server responds.  This will read until the end of the HTTP response header.
# task is a CkTask
set task [CkSocket_ReceiveUntilMatchAsync $tlsRead "\r\n\r\n"]
CkTask_Run $task

# Now send the request.  This should not block because the read is happening on the tlsRead object.
set httpGetReq "GET / HTTP/1.1\r\nHost: www.chilkatsoft.com\r\n\r\n"
set success [CkSocket_SendString $tlsWrite $httpGetReq]
# Assuming success for the example...

# Wait for the read task to finish.
# The 1/0 returned by Wait applies to the Wait method call, not the task.
set maxWaitMs 5000
set success [CkTask_Wait $task $maxWaitMs]
if {expr !$success  ||  [expr [[CkTask_get_StatusInt $task] != 7]  ||  [[CkTask_get_TaskSuccess $task] != 1]]} then {
    if {!$success} then {
        # The task.LastErrorText applies to the Wait method call.
        puts [CkTask_lastErrorText $task]
    }     else {
        # The ResultErrorText applies to the underlying task method call (i.e. the Connect)
        puts [CkTask_status $task]
        puts [CkTask_resultErrorText $task]
    }

    delete_CkTask $task

    delete_CkSocket $tlsWrite

    delete_CkSocket $tlsRead
    exit
}

# Examine the received HTTP response header:
puts "HTTP response header:"
puts [CkTask_getResultString $task]

# We should get a response that looks like this:
# 	HTTP response header:
# 	HTTP/1.1 200 OK
# 	Cache-Control: private
# 	Content-Length: 7477
# 	Content-Type: text/html
# 	Server: Microsoft-IIS/8.5
# 	Set-Cookie: ASPSESSIONIDSWDSTRTQ=BBNMIKGCHFJNILFFPLDIOGDE; secure; path=/
# 	X-Powered-By: ASP.NET
# 	X-Powered-By-Plesk: PleskWin
# 	Date: Thu, 06 Apr 2017 12:03:30 GMT

delete_CkTask $task

delete_CkSocket $tlsWrite

# Forget about the remainder of the HTTP response... The example was only to demonstrate
# simultaneous reading/writing..
set maxWaitMs 20
CkSocket_Close $tlsRead $maxWaitMs

delete_CkSocket $tlsRead