New features in SMTP and SSL library allow sending e-mail through Gmail

Although I added SSL support to Factor's I/O library recently, it was missing a feature needed by SMTP-TLS: upgrading insecure connections to secure ones. Unlike HTTPS, where the client connects to a special port number initiates a secure handshake as soon as the connection is established, SMTP uses a STARTTLS command, which is sent in plain-text, and handshaking only begins after this command is sent.

To accomodate this use-case, I added two new words to the io.sockets.secure vocabulary: send-secure-handshake and accept-secure-handshake. They are meant to be used in a client and server respectively, wishing to upgrade the current connection to a secure connection.

I also updated the smtp vocabulary to support the STARTTLS and AUTH PLAIN features of the SMTP protocol. The end result is that the SMTP vocabulary can now send e-mail through Gmail's SMTP servers. An example is shown below. The key thing to notice here is that we set the smtp-auth and smtp-tls? variables before sending the e-mail. As you can see, the SMTP library is easy to use and the code for sending an e-mail is succinct; we create an e-mail object, fill in some slots, and send it off:

"smtp.gmail.com" 587 <inet> smtp-server set
smtp-tls? on
"YourUserName@gmail.com" "YourPassword" <plain-auth> smtp-auth set

<email>
    "yourname@example.com" >>from
    { "theirname@example.com" } >>to
    "We should probably beer" >>subject
    "For teh win" >>body
send-email

The SMTP library is still missing some functionality, like support for character encodings, attachements and setting custom headers; I'll be adding those over time.