There are three standard types of messages used by the official client: instant messages (text), typing notifications, and application invitations. Each type of message is differentiated by a unique Content-Type field in the header. Clients may send messages with nonstandard content types for special features such as encryption and feature negotiation. The official client ignores all messages with nonstandard content types, and therefore all clients should as well. In addition, the official client completely ignores malformed messages: e.g. a message without a MIME header.
Instant messages, also known as plaintext messages, are the regular messages sent back and forth on MSN. They are sent with either Content-Type: text/plain or Content-Type: text/plain; charset=UTF-8 (each specify a different message encoding). Because the explanation for this type of message is quite long, it is fully explained in the Plaintext page.
A typing notification is sent to inform the other participants in a switchboard session that you are currently typing a message.
Content-Type: text/x-msmsgscontrol. It must not include charset=UTF-8.TypingUser field in the header. Its value should be your account name.\r\n).Below is an example of a typing message (just the payload, not the MSG line):
MIME-Version: 1.0\r\n
Content-Type: text/x-msmsgscontrol\r\n
TypingUser: example@passport.com\r\n
\r\n
\r\n
TypingUser field, it may display that value instead of your display name for the principal who is typing a message. Third party clients should just ignore the value of this field and use the source of the MSG to determine who is typing the message.Application invitations are used to invite principals to join applications such as file transfer, voice conversation, video conferencing, NetMeeting, remote assistance, whiteboard, games, and more. Invitations use Content-Type: text/x-msmsgsinvite; charset=UTF-8 and the charset parameter is not optional. Because the explanation for this type of message is quite long, it is fully explained in the Invitations page.
If you write your own MSN Messenger client, you can send any type of message you like, which will just be ignored by the official client. If you choose to do this, you're encouraged to write up a specification for your new message type so that others can use it too. Please contact us with a name, URL, and brief description of your entry so we can add it to this page.
At present, we know about the following proposals for unofficial message types: