(Swift 3,4,5...) Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method.

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let sock = CkoSocket()!

    // --------------------------------------------------------------------
    // 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.
    var useTls: Bool = true
    var port: Int = 4243
    var maxWaitMs: Int = 5000
    var success: Bool = sock.connect("tcpbin.com", port: port, ssl: useTls, maxWaitMs: maxWaitMs)
    if success == false {
        print("\(sock.lastErrorText!)")
        return
    }

    // 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:
    print("TLS version: \(sock.tlsVersion!)")

    sock.close(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 false, so we only have a simple TCP connection after this call.
    useTls = false
    success = sock.connect("tcpbin.com", port: port, ssl: useTls, maxWaitMs: maxWaitMs)
    if success == false {
        print("\(sock.lastErrorText!)")
        return
    }

    // 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.)
    success = sock.convertToSsl()
    if success == false {
        print("\(sock.lastErrorText!)")
        return
    }

    // OK, we now have a TLS connection.
    // Again, we can see the TLS version:
    print("TLS version: \(sock.tlsVersion!)")

    sock.close(maxWaitMs)

}