Visual FoxPro

Upgrade a Plain TCP Connection to TLS

Demonstrates Socket.ConvertToSsl, which upgrades an already-connected plain TCP socket to TLS by performing a client-side TLS handshake over the existing connection.

Background. This supports STARTTLS-style upgrades, where a protocol begins in plaintext and switches to TLS at a defined point. Perform the protocol-specific negotiation first, then call ConvertToSsl.

Chilkat Visual FoxPro Downloads

Download Chilkat for Visual FoxPro

Visual FoxPro

LOCAL lnSuccess
LOCAL loSocket
LOCAL lnBTls
LOCAL lnMaxWaitMs

lnSuccess = 0

loSocket = CreateObject('Chilkat.Socket')

*  Connect as plain TCP (no TLS yet).
lnBTls = 0
lnMaxWaitMs = 5000
lnSuccess = loSocket.Connect("example.com",5000,lnBTls,lnMaxWaitMs)
IF (lnSuccess = 0) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

*  At the point where the application protocol permits a STARTTLS-style upgrade, perform any required
*  negotiation, then upgrade the existing connection to TLS with a client-side handshake.
lnSuccess = loSocket.ConvertToSsl()
IF (lnSuccess = 0) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

? "Connection upgraded to TLS."

RELEASE loSocket