Visual FoxPro

Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method. Visual FoxPro

LOCAL lnSuccess
LOCAL loSock
LOCAL lnUseTls
LOCAL lnPort
LOCAL lnMaxWaitMs

lnSuccess = 0

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

loSock = CreateObject('Chilkat.Socket')

* --------------------------------------------------------------------
* 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.
lnUseTls = 1
lnPort = 4243
lnMaxWaitMs = 5000
lnSuccess = loSock.Connect("tcpbin.com",lnPort,lnUseTls,lnMaxWaitMs)
IF (lnSuccess = 0) THEN
    ? loSock.LastErrorText
    RELEASE loSock
    CANCEL
ENDIF

* 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:
? "TLS version: " + loSock.TlsVersion

loSock.Close(lnMaxWaitMs)

* ---------------------------------------------------------------------
* 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.
lnUseTls = 0
lnSuccess = loSock.Connect("tcpbin.com",lnPort,lnUseTls,lnMaxWaitMs)
IF (lnSuccess = 0) THEN
    ? loSock.LastErrorText
    RELEASE loSock
    CANCEL
ENDIF

* 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.)
lnSuccess = loSock.ConvertToSsl()
IF (lnSuccess = 0) THEN
    ? loSock.LastErrorText
    RELEASE loSock
    CANCEL
ENDIF

* OK, we now have a TLS connection.
* Again, we can see the TLS version:
? "TLS version: " + loSock.TlsVersion

loSock.Close(lnMaxWaitMs)

RELEASE loSock